As filed with the Securities and Exchange Commission on June 23, 2026.

Registration No. 333-_______

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

____________________________________

Form F-4
REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

____________________________________

WISeSat.Space Holdings Corp.

Co-registrant is listed on the following page
(Exact name of registrant as specified in its charter)

____________________________________

WISeSat.Space Holdings Corp.
Craigmuir Chambers, Road Town
Tortola, British Virgin Islands VG1110
Tel: +41-22-594-3000
(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

____________________________________

Puglisi & Associates

850 Library Ave., Suite 204

Newark, DE 19711

Tel: (302) 738-6680

(Name, address, including zip code, and telephone number, including area code, of agent for service)

____________________________________

Copies of all correspondence to:

____________________________________

Approximate date of commencement of proposed sale to the public: As soon as practicable after this registration statement is declared effective and all other conditions to the business combination described in the enclosed proxy statement/prospectus have been satisfied or waived.

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If applicable, place an X in the box to designate the appropriate rule provision relied upon in conducting this transaction:

Exchange Act Rule 13e-4(i) (Cross-Border Issuer Tender Offer) ☐

Exchange Act Rule 14d-1(d) (Cross-Border Third-Party Tender Offer) ☐

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933.

Emerging growth company ☒

If an emerging growth company that prepares its financial statements in accordance with U.S. GAAP, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

____________

†        The term “new or revised financial accounting standard” refers to any update issued by the Financial Accounting Standards Board to its Accounting Standards Codification after April 5, 2012.

The Registrant and Co-registrant hereby amend this registration statement on such date or dates as may be necessary to delay its effective date until the Registrant and Co-registrant shall file a further amendment that specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

CO-REGISTRANT TABLE

____________

(1)      The Co-Registrant has the following principal executive office:

Craigmuir Chambers, Road Town

Tortola, British Virgin Islands VG1110

Tel: +41-22-594-3000

(2)      The agent for service for the Co-Registrant is: Puglisi & Associates

850 Library Ave., Suite 204

Newark, DE 19711

Tel: (302) 738-6680

The information in this preliminary proxy statement/prospectus is not complete and may be changed. The registrant may not sell the securities described herein until the registration statement filed with the Securities and Exchange Commission is declared effective. This preliminary proxy statement/prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

After the Effective Time, from the Exchange Shares which WISeKey has received in the Business Combination, WISeKey may, in its sole discretion, distribute to its own shareholders a number of such shares in an amount up to ten percent (10%) of the total Exchange Shares, and CAC will, and will cause its Representatives to, reasonably cooperate with any such distribution. Any officers or directors of Pubco, or holders of five percent (5%) or more of issued and outstanding Pubco Ordinary Shares immediately prior to such distribution, who participate in receipt of such Exchange Shares distributed by WISeKey to its shareholders, have agreed to execute and deliver to the WISeKey and CAC a lock-up agreement limiting resales of such distributed shares for six months following the closing of the Business Combination, subject to certain exceptions provided therein.

Each of CAC, Pubco and the Company have agreed in connection with the Business Combination to use commercially reasonable efforts to seek and enter into financing agreements for an aggregate of at least $10 million in proceeds having such terms as CAC and the Company shall mutually agree (collectively, the “Transaction Financing”). As of the date of this proxy statement/prospectus, SEALSQ Corp (Nasdaq: LAES) (“SEALSQ”), a subsidiary of WISeKey, has provided $10 million in Transaction Financing, which has been made into the Company or its subsidiaries prior to Closing.

This proxy statement/prospectus covers the registration of up to 31,385,052 Pubco Ordinary Shares in connection with the Business Combination. The CAC Units, CAC Ordinary Shares, and CAC Rights are currently listed on the Nasdaq Stock Market LLC (“Nasdaq”) under the symbols “COLAU,” “COLA” and “COLAR,” respectively. As a result of the Business Combination, such securities will cease trading on Nasdaq and will be deregistered under the Securities Exchange Act of 1934, as amended. If Pubco’s application for listing is approved, Pubco Ordinary Shares are expected to be traded on Nasdaq upon the consummation of the Business Combination under the symbol “WSAT.” It is a condition of the consummation of the Business Combination that the Pubco Ordinary Shares are approved for listing on Nasdaq, subject only to official notice of issuance thereof.

At the extraordinary general meeting, CAC shareholders will be asked to consider and vote upon the following proposals:

•        Proposal No. 1 — The NTA Proposal — to consider and vote upon a proposal to approve by special resolution, the amendment of the CAC Articles, which currently restricts consummation of a shareholder redemption offer in connection with a business combination if the redemptions made pursuant to such offer would cause CAC to have net tangible assets of less than US$5,000,001 prior to or upon consummation of a business combination (the “NTA Requirement”) as set out in Articles 37.2, 37.5, 37.6 and 37.8 of the CAC Articles, in order to expand the methods that CAC may employ to not become subject to the “penny stock” rules of the SEC, immediately prior to the Effective Time (as defined in the Plan of Merger) (the “NTA Proposal”);

•        Proposal No. 2 — The Business Combination Proposal — to consider and vote upon a proposal to approve and authorize, by ordinary resolution, the Business Combination Agreement, dated as of November 9, 2025 (as amended from time to time), by and among Columbus Acquisition Corp, WISeSat.Space Holdings Corp., a British Virgin Islands business company (“Pubco”), WISeSat Merger Sub Corp., a Cayman Islands exempted company and a wholly owned subsidiary of Pubco (“Merger Sub”), WISeSat.Space Corp., a British Virgin Islands business company (the “Company”), WISeKey International Holding Ltd., a Swiss company (“WISeKey” and together with its successors and permitted assigns, and any holders of Company Ordinary Shares or Company Class F Shares immediately prior to the Effective Time, collectively, the “Seller”), a copy of which is attached to this proxy statement/prospectus as Annex A, and the transactions contemplated therein, which we refer to as the “Business Combination”;

•        Proposal No. 3 — The Merger Proposal — to consider and vote upon a proposal to approve and authorize, by special resolution, that (a) CAC merge with Merger Sub so that Merger Sub will merge with and into CAC and CAC will be the surviving company and all the undertaking, property and liabilities of the Merger Sub vest in CAC by virtue of such merger pursuant to the Companies Act (As Revised); (b) the Plan of Merger substantially in the form annexed to this Proxy Statement as Annex A-1 be and is hereby authorized, approved and confirmed in all respects and CAC be authorized to enter into the Plan of Merger; (c) that upon the Effective Time (as defined in the Plan of Merger): (i) the amending and restating of the memorandum and articles of CAC as the surviving company of the Merger is approved in all respects, (ii) the board of directors and executive officers of CAC resign and the board of directors and the executive officers of Merger Sub immediately prior to the Effective Time become the board of directors and executive officers of the Surviving Company; and (iii) the authorized share capital of CAC

(as the surviving company of the Merger) shall be amended such that firstly, all authorized preference shares of par value US$0.0001 each shall be redesignated as authorized ordinary shares of a par value of US$0.0001 each, such that the authorized share capital of CAC (as the surviving company of the Merger) shall be US$50,000 divided into 500,000,000 ordinary shares of a par value of US$0.0001 each (the “Redesignation”); secondly, upon the Redesignation becoming effective, the authorized share capital of CAC (as the surviving company of the Merger) shall be consolidated and divided so as to become US$50,000 divided into 5,000,000 ordinary shares of a par value of $0.01 each (the “Share Consolidation”); and thirdly (iii) upon the Share Consolidation becoming effective, the authorized share capital of CAC (as the surviving company of the Merger) shall be decreased from $50,000 divided into 5,000,000 ordinary shares of a par value of $0.01 each to $1 divided into 100 ordinary shares of a par value of $0.01 each;

•        Proposal No. 4 — The Pubco Equity Plan Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, the adoption of a new equity incentive plan (the “Pubco Equity Plan”) by Pubco (the “Pubco Equity Plan Proposal”). A copy of the Pubco Equity Plan is attached to the accompanying proxy statement/prospectus as Annex D;

•        Proposal No. 5 — The ESPP Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, the adoption of an employee share purchase program (the “Employee Share Purchase Program”) by Pubco (the “ESPP Proposal”). A copy of the Pubco Equity Plan is attached to the accompanying proxy statement/prospectus as Annex E;

•        Proposal No. 6 — The Nasdaq Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, for purposes of complying with applicable listing rules of The Nasdaq Stock Market, the issuance of up to an aggregate of 31,385,052 Pubco Ordinary Shares, no par value, in connection with the Merger and the Share Exchange (the “Nasdaq Proposal”);

•        Proposal No. 7 — The Pubco Director Election Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, that seven directors be elected to serve terms on Pubco’s board of directors effective at the Closing (the “Pubco Director Election Proposal”); and

•        Proposal No. 8 — The Adjournment Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, the adjournment of the extraordinary general meeting to a later date or dates, if necessary or appropriate, to permit further solicitation and vote of proxies in the event that there are insufficient votes for, or otherwise in connection with, the NTA Proposal, the Business Combination Proposal, the Merger Proposal, the Pubco Equity Plan Proposal, the ESPP Proposal, the Nasdaq Proposal, or the Pubco Director Election Proposal (the “Adjournment Proposal”).

The CAC board of directors (the “CAC Board”) received a fairness opinion from Newbridge Securities Corporation (“Newbridge”) as to the fairness of the transactions to the holders of CAC Ordinary Shares from a financial point of view. See “Proposal No. 2 — The Business Combination Proposal — Fairness Opinion of Newbridge” and the opinion of Newbridge included as Annex B to this proxy statement/prospectus. As permitted under the CAC Articles (as defined herein) and the Companies Act (Revised) of the Cayman Islands, the independent directors of CAC did not retain an unaffiliated representative to act solely on behalf of unaffiliated securityholders of CAC for purposes of negotiating the terms of the Business Combination Agreement and/or preparing a report concerning the approval of the Business Combination.

After careful consideration, each of the CAC Board and WISeKey’s board of directors has unanimously approved the Business Combination Agreement and determined that each of the proposals is fair to and it is advisable to consummate the Business Combination. The CAC Board unanimously recommends that the CAC Shareholders vote FOR all of the proposals presented to the shareholders at the extraordinary general meeting. The Transactions were not structured to require the approval of at least a majority of unaffiliated securityholders of CAC, as permitted under the CAC Articles and the Companies Act (Revised) of the Cayman Islands. When you consider the CAC Board’s recommendation of these proposals, you should keep in mind that Hercules Capital Management VII Corp (the “Sponsor”) and CAC’s directors and officers have interests in the Transactions that may conflict with your interests as a shareholder.

Dr. Fen “Eric” Zhang is the sole director and the chief executive officer of the Sponsor and has voting, dispositive or investment powers over the Sponsor with respect to CAC Ordinary Shares held by the Sponsor, thus is deemed to have beneficial ownership of the shares held by the Sponsor. The Sponsor currently holds (i) 1,464,000 CAC Ordinary Shares, (ii) 234,290 CAC Ordinary Shares underlying the CAC Private Units; and (iii) 33,470 CAC Ordinary Shares underlying the CAC Private Rights.

Each of the two current and one former independent directors of CAC holds 12,000 CAC Ordinary Shares, for a total of 36,000 CAC Ordinary Shares collectively. Additionally, one current independent director of CAC has an option to receive CAC Ordinary Shares consisting of 12,000 CAC Ordinary Shares pursuant to a share purchase option dated March 20, 2025, and which we refer to as Director Option Shares. None of the officers or directors of CAC have received any cash compensation for services rendered to CAC or in connection with the Business Combination. At the Closing, the directors of CAC which hold CAC Ordinary Shares are expected to hold Pubco Ordinary Shares converted in the Business Combination for those CAC Ordinary Shares.

At the Closing, the Sponsor is expected to hold 1,731,760 Pubco Ordinary Shares, as a result of the Merger consisting of (i) 1,464,000 Pubco Ordinary Shares to be converted from CAC Ordinary Shares held by the Sponsor, (ii) 234,290 Pubco Ordinary Shares to be converted from CAC Ordinary Shares underlying the CAC Private Units held by the Sponsor; and (iii) 33,470 Pubco Ordinary Shares to be converted from CAC Rights underlying the CAC Private Units held by the Sponsor. The Sponsor did not and will not receive any cash compensation during the ordinary course of managing CAC or in connection with the Business Combination, other than $10,000 per month for office space, administrative and support services, as described below.

The following table sets forth the amount of consideration received or to be received by (1) the Seller, (2) CAC Public Shareholders, (3) the holders of CAC Public Rights, (4) the Sponsor, and (5) the CAC IPO Underwriter, in connection with the Business Combination, in each case, assuming no redemptions, 50% redemptions, and maximum redemptions, which, and in each scenario, assumes a per share value of $10.00. Unless otherwise specified, the share amounts have been determined under the assumptions set forth under the section of this proxy statement/prospectus entitled “Frequently Used Terms.” If the actual facts are different from the foregoing assumptions, the share amounts and cash value set forth below will be different.

____________

(1)      The value of the consideration to be received is calculated based on a deemed value of $10.00 per Pubco Ordinary Shares.

(2)      Represents the number of CAC Ordinary Shares included in the Private Units, which will be converted into Pubco Ordinary Shares on a one-on-one basis.

(3)      Represents the maximum number of CAC Ordinary Shares upon conversion of the Private Rights, which will be converted into Pubco Ordinary Shares on a one-on-one basis. Every seven (7) Private Rights will be converted to one CAC Ordinary Share.

(4)      Represents the number of CAC Ordinary Shares held by two current directors and one former director of CAC (excluding the shares in the event of exercise of the share purchase option held by Mr. Cameron R. Johnson described in the subsequent note).

(5)      Represents 12,000 Founder Shares to be transferred from the Sponsor to Mr. Cameron R. Johnson, one of CAC’s directors, pursuant to a share purchase option agreement dated March 20, 2025, subject to specified terms and conditions therein.

(6)      Represents the maximum number of CAC Ordinary Shares upon conversion of the CAC Public Rights, which will be converted into Pubco Ordinary Shares on a one-on-one basis. Every seven (7) CAC Public Rights will be converted to one CAC Ordinary Share.

(7)      Represents 18,387,652 Company Ordinary Shares and 12,997,400 Company Class F Shares that are held by the WISeSat shareholders who will have their shares in WISeSat exchanged for Pubco Ordinary Shares and Pubco Class F Shares, respectively, as a result of the Share Exchange. Such shares as a result of such Share Exchange include 650,000 Pubco Ordinary Shares exchanged for shares held by Maxim Partners LLC, an affiliate of Maxim Group LLC, received for payment of its fees as Seller’s merger & acquisitions (“M&A”) advisor.

(8)      Assumes that Pubco Class F Shares are not converted into Pubco Ordinary Shares. Pubco Class F Shares are convertible at the option of the holder on a one for one basis into Pubco Ordinary Shares. For more information about such Pubco Class F Shares, see “Description of Pubco’s Securities.” If Pubco Class F Shares were fully converted then the number of Pubco Ordinary Shares would be the number reflected on the foregoing row in the table, being “Total Shares” beginning with 31,385,052.

Compensation Received by the Sponsor

Set forth below is a summary of the terms and amount of the compensation received or to be received by CAC’s sponsor, Hercules Capital Management VII Corp (the “Sponsor”) its affiliates and promoters in connection with the Business Combination or any related financing transaction, the amount of securities issued or to be issued by CAC to the Sponsor and its affiliates and the price paid or to be paid for such securities or any related financing transaction.

The amount of the compensation received or to be received by the Sponsor, its affiliates, and promoters in connection with the Business Combination or any related financing transaction; the amount of securities issued or to be issued by CAC to the Sponsor, its affiliates, and promoters; and the price paid or to be paid for such securities in connection with the Business Combination or any related financing transaction will not result in a material dilution of the equity interests of non-redeeming shareholders who hold the securities until the consummation of the de-SPAC transaction. See “Unaudited Pro Forma Condensed Combined Financial Information.”

Dual Class of Pubco Shares

As described above, at the Closing of the Business Combination, the existing Company Ordinary Shares will be exchanged for Pubco Ordinary Shares, and the Company Class F Ordinary Shares will be exchanged for Pubco Class F Shares, in each case in the Share Exchange. As a result following the Closing, the outstanding Pubco Shares will be comprised of two separate classes, namely, Pubco Ordinary Shares and Pubco Class F Shares. The Pubco Ordinary Shares and Pubco Class F Shares (together the “Pubco Shares”) vote together on all matters subject to a vote of the holders of Pubco Ordinary Shares.

The total consideration issued in the Closing of the Business Combination to the Seller, as described above, consists of Pubco Shares equal to $250 million plus Transaction Financing (expected to be at least $10 million), divided by $10 per share, which would equal 26 million Pubco Shares, and the total of the Pubco Ordinary Shares and Pubco Class F Shares, in aggregate, issued at the Closing to shareholders of the Seller will equal that same number of aggregate Pubco Shares.

Company Class F Ordinary Shares are only held by WISeKey and its subsidiary, SEALSQ. As a result, the Pubco Class F Shares exchanged for such shares in the Business Combination will only be held by WISeKey and SEALSQ. The Pubco Class F Shares are non-transferable (except to an affiliates of the holder). Each of WISeKey and SEALSQ have entered into a voting agreement that provides that all holders of Pubco Class F Shares will vote in accordance with the majority holder of Pubco Class F Shares (the “Class F Shareholders Agreement”), which as of the date of this proxy statement/prospectus is WISeKey. Each Pubco Class F Share entitles the holder to a number of votes per share that results in the Pubco Class F Shares as a class in the aggregate representing 49.99% of the total voting power of Pubco Shares.

Immediately after the Business Combination, WISeKey is expected to own at least 75% of the outstanding Pubco Ordinary Shares and Pubco Class F Shares (consisting of 29% of outstanding Pubco Ordinary Shares and 46% of outstanding Pubco Class F Shares), assuming no redemption of publicly traded CAC Ordinary Shares by its shareholders. For more information, see “Summary of the Proxy Statement/Prospectus — Unaudited Pro Forma Condensed Combined Financial Information.” However, WISeKey in any event will hold not less than 49.99% of the total voting power of Pubco Shares, as a result of such voting rights of Pubco Class F Shares and the Class F Shareholders Agreement, as long as it holds a majority of Pubco Class F Shares, notwithstanding any subsequent sales by WISeKey of Pubco Ordinary Shares.

Accordingly, immediately after the Business Combination, WISeKey would have substantial voting power both by holding over 75% of the outstanding Pubco Shares and also being the majority owner of Pubco Class F Shares. Due to the nature of the voting power of the Pubco Class F Shares, WISeKey may be entitled to retain 49.99% of the voting power while reducing, potentially significantly, its economic interest in Pubco Shares. For more information about voting thresholds under applicable law of the British Virgin Islands, see “Description of Pubco’s Securities.”

The only other owner of Pubco Class F Shares is WISeKey’s subsidiary, SEALSQ, and because such shares are non-transferable (except to affiliates of the holders), only SEALSQ would be able to exercise such voting power, if WISeKey no longer held a majority of the outstanding Pubco Class F Shares. WISeKey would no longer hold a majority of the outstanding Pubco Class F Shares (and SEALSQ would hold such voting power) if either WISeKey transferred such shares to its affiliate, converted its Pubco Class F Shares such that it held less than a majority of such shares, or a change of control of WISeKey occurred. The Pubco Class F Shares are convertible by the shareholder on a 1 for 1 basis into Pubco Ordinary Shares. The amended and restated memorandum and articles of association of Pubco at Closing provides that if either WISeKey or SEALSQ experienced a change of control (defined as acquisition by any person or entity, alone or jointly, of more than 50% of the voting rights of any shareholder of Pubco Class F Shares which is a corporate entity or otherwise determined by Pubco’s board directors) then the person acquiring control of WISeKey or SEALSQ would not hold Pubco Class F Shares, but immediately prior to such change of control each Pubco Class F Share held by such person subject to such change of control would automatically be redeemed in exchange for one Pubco Ordinary Share and thereafter such Pubco Class F Shares held by such person would cease to exist. If there was a change of control of WISeKey, SEALSQ or their affiliate would be sole holder of Pubco Class F Shares and the right to exercise the voting power of outstanding Pubco Class F Shares. This redemption provision could also have an effect of limiting or impeding a change of control of WISeKey or SEALSQ, and would prevent a person from gaining majority control of Pubco by acquisition of securities in WISeKey or SEALSQ. For more information see “Risk Factors — Although WISeKey immediately after the Business Combination would own over 50% of Pubco Ordinary Shares, WISeKey’s ownership of Pubco Class F Shares separately would give WISeKey voting power of at least 49.99% of Pubco Shares, allowing WISeKey to hold significant voting power as long as it holds Pubco Class F Shares, even if it significantly reduced its holdings of Pubco Ordinary Shares.”

Conflicts of Interest

CAC

When considering the CAC Board’s recommendation that CAC’s shareholders vote in favor of the Business Combination Proposal and the Merger Proposal, shareholders should be aware that directors and officers of CAC may have interests in the Business Combination that are different from, or in addition to, the interests of unaffiliated shareholders of CAC. CAC’s CEO and Chairman, Dr. Fen “Eric” Zhang, is also the sole director and the chief executive officer of the Sponsor. These interests include, among other things, the interests listed below:

•        the fact that immediately following the consummation of the Business Combination, the initial shareholders are expected to hold 1,977,760 Pubco Ordinary Shares on an as-converted basis, consisting of (i) 1,464,000 Pubco Ordinary Shares to be converted from CAC Ordinary Shares held by the Sponsor, (ii) 234,290 Pubco Ordinary Shares to be converted from CAC Ordinary Shares underlying the CAC Private Units held by the Sponsor; (iii) 33,470 Pubco Ordinary Shares to be converted from CAC Rights underlying the CAC Private Units held by the Sponsor; (iv) 36,000 Pubco Ordinary Shares to be converted from CAC Ordinary Shares underlying the CAC Private Units held by CAC’s former and current directors and (v) 210,000 Pubco Ordinary Shares to be held by CAC IPO Underwriter, which in the aggregate, would be approximately 7% and 7% ownership interest in the Pubco following the consummation of the Business Combination under the no redemption scenario and the maximum redemption scenario, respectively, on an as converted basis.

•        the fact that the Sponsor acquired 234,290 CAC Private Units at $10.00 per private unit through private placement simultaneously with the closing of CAC IPO on January 24, 2025.

•        the fact that the Sponsor paid $25,000, or approximately $0.0001 per share, for 1,725,000 Founder Shares prior to CAC IPO, which will be canceled and convert automatically, on a one-for-one basis, into the same number of Pubco Ordinary Shares at the Effective Time pursuant to the Business Combination Agreement. All of the Founder Shares are subject to certain transfer restrictions and could have a significantly higher value at the time of the Business Combination, which if unrestricted and freely tradable would be valued at approximately $[•] million, based on the most recent closing price of CAC Ordinary Shares of $[•] per share on [•], 2026.

•        the fact that if the Business Combination or another business combination is not consummated by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles), CAC will cease all operations except for the purpose of winding up, redeeming 100% of outstanding Public Shares for cash and, subject to the approval of CAC’s remaining shareholders and the CAC Board, liquidating and dissolving. In such event, the Founder Shares and Private Shares held by the Sponsor would be worthless because CAC’s initial shareholders are not entitled to participate in any redemption or distribution with respect to such shares.

•        the fact that if the Business Combination is consummated, each of issued and outstanding CAC Ordinary Shares will be converted into one Pubco Ordinary Share. Given the differential in the purchase price that the Sponsor paid for the Founder Shares, as compared to the price of CAC Public Shares paid by CAC Public Shareholders in the CAC IPO and the substantial number of Pubco Ordinary Shares that the Sponsor will receive upon conversion of the Founder Shares, the Sponsor is likely to be able to recoup their investment in CAC and make a substantial profit on that investment, even if Pubco Ordinary Shares have lost significant value. This means that the Sponsor could earn a positive rate of return on their investment, even if CAC Public Shareholders experience a negative rate of return in the Pubco following the consummation of the Business Combination.

•        the fact that the Sponsor and officers and directors of CAC have agreed to waive their rights to liquidating distributions from the Trust Account with respect to any insider shares and private shares held by them if CAC fails to complete an initial business combination by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles).

•        the fact that if CAC liquidates the Trust Account prior to the consummation of a business combination, it will be liable to pay debts and obligations to target businesses or vendors or other entities that are owed money by CAC for services rendered or contracted for or products sold to us in excess of the net proceeds of CAC IPO not held in the Trust Account, but only to the extent necessary to ensure that such debts or obligations do not reduce the amounts in the trust account and only if such parties have not executed a waiver agreement.

•        the fact that pursuant to the Business Combination Agreement, the Sponsor shall promptly provide 50% of the payments, including the amount payable for each monthly extension, made by CAC to the Trust Account (the “Extension Payments”) to extend the deadline for the consummation of CAC’s initial business combination and to incentivize Public Shareholders not to redeem their CAC Ordinary Shares by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles).

•        the fact that CAC’s Sponsor, officers, directors, or their affiliates may, but are not obligated to, loan CAC funds as may be required (“Working Capital Loan”) to fund working capital deficiencies or finance transaction costs in connection with an initial business combination. Up to $3,000,000 of such Working Capital Loan may be convertible upon consummation of our business combination into private CAC Units at $10.00 per unit at the option of the lender.

•        the fact that the Sponsor is entitled to $10,000 per month for office space, administrative and support services for up to 12 months following the CAC IPO.

•        the fact that the Business Combination Agreement provides for the continued indemnification of CAC’s former and current directors and officers and the continuation of directors and officers liability insurance covering CAC’s former and current directors and officers.

•        the fact that CAC’s officers and directors and their affiliates are entitled to reimbursement of out-of-pocket expenses incurred by them in connection with certain activities on CAC’s behalf, such as identifying and investigating possible business targets and business combinations. However, if CAC fails to consummate a business combination within the required time period under the CAC Articles, these persons will not have any claim against the Trust Account for reimbursement. Accordingly, CAC may not be able to reimburse these expenses if the Business Combination with Pubco or another business combination is not completed by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles).

•        the fact that WISeSat.Space Holdings, the Sponsor and Pubco will enter into an amendment to the Registration Rights Agreement of CAC on or prior to the Closing which provides for registration rights following consummation of the Business Combination.

•        the fact that in addition to these interests of the Sponsor and CAC’s officers, directors and advisors, to the fullest extent permitted by applicable laws and CAC’s memorandum and articles of association, waive certain applications of the doctrine of corporate opportunity in some circumstances where the application of any such doctrine would conflict with any fiduciary duties or contractual obligations they may have, and CAC will renounce any expectation that any of its directors or officers will offer any such corporate opportunity of which he or she may become aware to us. CAC does not believe that the pre-existing fiduciary duties or contractual obligations of its officers and directors materially impacted its search for an acquisition target. Further, CAC does not believe that the waiver of the application of the corporate opportunity doctrine had a material impact on its ability to complete its initial business combination.

•        the fact that the fees payable to Maxim Group LLC are contingent upon the successful closing of the Business Combination. As a result, Maxim may have an incentive to ensure the closing of the transaction even if the terms are not favorable to CAC shareholders.

For a discussion of all potential sources of conflicts of interests, see “Interests of the Sponsor and CAC’s Directors and Officers in the Business Combination.”

Company

Certain officers and directors of the Company and its affiliates, including WISeKey, have interests in the Business Combination that may differ from, or be in conflict with, the interests of unaffiliated shareholders of CAC. Following the consummation of the Business Combination, certain officers and directors of the Company and Pubco are expected to continue to serve as officers, directors or affiliates of WISeKey and/or other Seller-related entities and, as a result, will continue to owe fiduciary duties and/or contractual obligations to such entities. These continuing relationships may create conflicts of interest when such individuals are making decisions on behalf of Pubco.

In addition, WISeKey and SEALSQ are expected to retain significant equity ownership and voting power in Pubco following the Business Combination, including through ownership of Pubco Class F Shares, which provide enhanced voting rights as described above. WISeKey is expected to hold approximately 75% of the Pubco Shares immediately following the Business Combination (assuming no redemptions by CAC public shareholders), although in any event either WISeKey or SEALSQ will hold not less than 49.99% of the total voting power of Pubco Shares (if either entity continues to hold Pubco Class F Shares), notwithstanding any of either of their subsequent sales of Pubco Ordinary Shares.

Pubco also expects to enter into, and continue to be subject to, various related-party arrangements with WISeKey and its subsidiaries and affiliates following the Business Combination. See “Certain Relationships and Related Party Transactions — Certain Transactions of the Company.” These relationships may result in benefits to WISeKey and its subsidiaries including SEALSQ that are not shared by unaffiliated CAC public shareholders and may influence the manner in which Pubco is operated following the Business Combination.

Voting Power of WISeKey

Immediately following the consummation of the Business Combination, WISeKey is expected to hold approximately 75% of the Pubco Shares (assuming no redemptions by CAC public shareholders), although in any event will hold at least 49.99% of the total voting power of Pubco Shares (if it continues to hold a majority of Pubco Class F Shares), notwithstanding any subsequent sales of Pubco Ordinary Shares. WISeKey’s holding of 75% of Pubco Shares consists of 29% of outstanding Pubco Ordinary Shares and 46% of outstanding Pubco Class F Shares, and both classes vote together as a single class on all matters submitted to a vote of holders of Pubco Ordinary Shares.

As described above, each Pubco Class F Share entitles the holder to a number of votes per share that results in the Pubco Class F Shares as a class in the aggregate representing 49.99% of the total voting power of Pubco Shares, and all the holders of Pubco Class F Shares, consisting of WISeKey and SEALSQ, have agreed to vote their shares in accordance with the holder of a majority of Pubco Class F shares, which as of the date of this proxy statement/prospectus is WISeKey.

If WISeKey converted a majority of Pubco Class F Shares into Pubco Ordinary Shares, then SEALSQ, a subsidiary of WISeKey, would have a majority of the Pubco Class F Shares and be able in lieu of WISeKey to determine the vote of Pubco Class F Shares, although because the Pubco Class F Shares are non-transferable only WISeKey or SEALSQ or such person’s affiliate would have such rights to hold Pubco Class F Shares. In the event of a change of control of WISeKey or SEALSQ, such entity would receive Pubco Ordinary Shares lieu of Pubco Class F Shares, at a rate of one to one, as an automatic redemption of their Pubco Class F Shares, which may serve to reduce the likelihood of a change of control of WISeKey or SEALSQ, and which would prevent any acquiror of control of WISeKey or SEALSQ from being able to hold Pubco Class F Shares. For more information, see “Pubco’s principal shareholder WISeKey has the ability to exert significant influence over important corporate matters that require approval of shareholders, which may deprive you of an opportunity to receive a premium for Pubco’s Ordinary Shares and reduce the value of your investment.”

Between March 21, 2024 and December 20, 2024, an aggregate of 1,725,000 founder shares were issued to the Sponsor for an aggregate purchase price of $25,000. Simultaneously with the closing of the IPO, CAC consummated the private placement (the “Private Placement”) with the Sponsor of 234,290 CAC Units (the “Private Unit(s)”), generating total proceeds of $2,342,900. The following table sets forth information regarding directors and officers of CAC and the Sponsor’s beneficial interests in securities of CAC as at [•]:

____________

Notes:

(1)      Unless otherwise noted, the business address of each of the following entities or individuals is c/o Columbus Acquisition Corp, 14 Prudential Tower, Singapore, 049712.

(2)      Dr. Fen “Eric” Zhang is the sole director and the chief executive officer of the Sponsor. The person having voting, dispositive or investment powers over the Sponsor is Dr. Fen “Eric” Zhang, thus Fen Zhang is deemed to have beneficial ownership of the shares held by the Sponsor.

If CAC does not consummate an initial business combination by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles), it will be required to dissolve and liquidate and the securities held by the Initial Shareholders will be worthless because the Initial Shareholders have agreed to waive their rights to any liquidation distributions. The 1,731,760 Pubco Ordinary Shares that will be received by the Sponsor, if unrestricted and freely tradable, would have had an aggregate market value of approximately $[•] million based upon the closing price of $[•] per share on Nasdaq on [•], 2026, the most recent practicable date prior to the date of this proxy statement/prospectus. As a result of the interests of the Sponsor and the directors and officers of CAC in securities of CAC, the Sponsor and the directors and officers of CAC

have an incentive to complete an initial business combination and may have a conflict of interest in the transaction, including without limitation, in determining whether a particular business is an appropriate business with which to effect the initial business combination of CAC.

Moreover, prior to the IPO, CAC issued an aggregate of 1,725,000 founder shares, or insider shares, to the Sponsor for an aggregate purchase price of $25,000. As of the date of this proxy statement/prospectus, the Initial Shareholders hold an aggregate of 1,944,290 CAC Ordinary Shares, including 1,464,000 founder shares with the purchase price of $25,000, or approximately $0.017 per share. As a result, Sponsor and the directors and officers of CAC will have rates of return on their respective investments which differ from the rate of return of shareholders of CAC who purchased CAC Ordinary Shares at various other prices, including CAC Ordinary Shares included in CAC Units that were sold at $10.00 per unit in the IPO. Upon the consummation of the Business Combination, among other things, each of the then issued and outstanding CAC Ordinary Shares will convert automatically, on a one-for-one basis, into one Pubco Ordinary Share. In the event the share price of Pubco Ordinary Shares falls below the price paid by a shareholder of CAC at the time of purchase of the CAC Ordinary Shares by such shareholder, a situation may arise in which the Sponsor, an officer or a director of CAC maintains a positive rate of return on its/his/her CAC Ordinary Shares while such shareholder of CAC experiences a negative rate of return on the shares such shareholder of CAC purchased. The securities currently owned by the Initial Shareholders will have a significantly higher value at the time of the Business Combination than at the time of purchase. For purpose of illustration, given that as of the date hereof, the Initial Shareholders hold 1,944,290 CAC Ordinary Shares, including 1,464,000 founder shares and 234,290 shares included in the Private Units, based on an estimated market price of $[•] per Pubco Ordinary Share (i.e. being the CAC Ordinary Shares closing price on [•], 2026, the most recent practicable date prior to the date of this proxy statement/prospectus) immediately after Closing, the aggregate value of Pubco Ordinary Shares owned by the Initial Shareholders would be $[•] and the Initial Shareholders would have a potential aggregate profit of $[•], representing a profit of $[•] per Pubco Ordinary Share, whereas other public shareholders of CAC would only have a profit of $[•] per Pubco Ordinary Share.

As a result of the interests of the Initial Shareholders in securities of CAC, the Initial Shareholders will benefit from the completion of the Business Combination and therefore may be incentivized to complete the Business Combination even if it is with a less favorable target company or on terms less favorable to shareholders of CAC, rather than liquidate. They may have a conflict of interest in the transaction, including without limitation, in determining whether a particular business is an appropriate business with which to effect the initial business combination of CAC.

In connection with the Business Combination, there may be any actual or potential material conflicts of interest between, on one hand, CAC’s officers or directors; and, on the other hand, unaffiliated security holders of CAC. Shareholders should also be aware that interests of CAC, CAC officers and directors may be inherently different from the interests of unaffiliated shareholders of CAC, which could cause them to pursue terms of Business Combination less favorable to non-redeeming shareholders, and they owe no fiduciary duty to CAC’s shareholders. However, under Cayman Islands law, the SPAC’s directors owe fiduciary duties to the SPAC, including a duty of loyalty, a duty to act honestly and a duty to act in what they consider in good faith to be in the best interests of the SPAC as a whole. The SPAC’s directors also must exercise their powers only for a proper purpose. Accordingly, when considering and approving the Business Combination, the SPAC’s directors must comply with their fiduciary duties under Cayman Islands law by acting honestly, in good faith, and in the best interests of the SPAC as a whole. After Closing, CAC has the right to designate one independent director to the board of Pubco. Furthermore, CAC intends to use substantially all of the funds held in the trust account to complete the Business Combination, after the payment to holders of CAC Ordinary Shares exercising redemption rights upon Closing, and any remaining amount will be used for future working capital and other corporate purposes of the combined entity. See “Questions and Answers about the Business Combination and the Extraordinary General Meeting — Q: What happens to the funds deposited in the Trust Account after consummation of the Business Combination?” on page xxiii.

The CAC Board has determined (i) that the terms and conditions of the Business Combination Agreement and the transactions contemplated thereby, including the Business Combination, are advisable, fair to and in the best interests of, CAC and its shareholders, and (ii) to recommend that the shareholders approve the transactions contemplated by the Business Combination Agreement, including the Business Combination. CAC obtained a fairness opinion from Newbridge in determining whether or not to proceed with the Business Combination. The CAC Board relied on the Fairness Opinion and also the financial skills and background of its officers and directors. CAC believed that the officers and directors of CAC have substantial experience in evaluating the operating and financial merits of companies from a wide range of industries and concluded that their experience and background enabled them to make the necessary analyses and determinations regarding the Business Combination. For details, see “Proposal No. 2 — The Business Combination Proposal — Fairness Opinion of Newbridge” on page 109.

Pubco will be an “emerging growth company” as defined in the JOBS Act and is therefore eligible to take advantage of certain reduced reporting requirements otherwise applicable to other public companies.

Pubco will also be a “foreign private issuer” as defined in the Exchange Act and will be exempt from certain rules under the Exchange Act that impose certain disclosure obligations and procedural requirements for proxy solicitations under Section 14 of the Exchange Act. In addition, Pubco’s officers, directors and principal shareholders will be exempt from the reporting and “short-swing” profit recovery provisions under Section 16 of the Exchange Act. Moreover, Pubco will not be required to file periodic reports and financial statements with the U.S. Securities and Exchange Commission as frequently or as promptly as U.S. companies whose securities are registered under the Exchange Act.

Pubco will be a “controlled company” as defined under the Nasdaq corporate governance rules, because one of Pubco’s shareholders, WISeKey, will hold more than 50% of its voting power. As a result, for so long as Pubco remains a controlled company as defined under those rules, Pubco is exempt from, and Pubco shareholders generally are not provided with the benefits of, some of the Nasdaq Stock Market corporate governance requirements, including that: a majority of its board of directors must be independent directors; its compensation committee must be composed entirely of independent directors; and its corporate governance and nomination committee must be composed entirely of independent directors.

The accompanying proxy statement/prospectus provides CAC shareholders with detailed information about the Business Combination Agreement and other matters to be considered at the extraordinary general meeting of CAC shareholders. We encourage you to read the entire accompanying proxy statement/prospectus, including the annexes and other documents referred to therein, carefully and in their entirety. You should also carefully consider the risk factors described in “Risk Factors” beginning on page 42 of the accompanying proxy statement/prospectus.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES REGULATORY AGENCY HAS APPROVED OR DISAPPROVED THE TRANSACTIONS DESCRIBED IN THIS PROXY STATEMENT/PROSPECTUS OR ANY OF THE SECURITIES TO BE ISSUED IN THE BUSINESS COMBINATION AGREEMENT, PASSED UPON THE MERITS OR FAIRNESS OF THE BUSINESS COMBINATION AGREEMENT OR RELATED TRANSACTIONS OR PASSED UPON THE ADEQUACY OR ACCURACY OF THE DISCLOSURE IN THIS PROXY STATEMENT/PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY CONSTITUTES A CRIMINAL OFFENSE.

As of March 31, 2026, there was approximately $26.84 million in CAC’s trust account. On [    ], 2026, the last sale price of one CAC Ordinary Share was $[    ].

Pursuant to CAC’s amended and restated memorandum and articles of association as adopted by special resolution dated January 17, 2025 and effective on January 22, 2025, and as amended on January 16, 2026 (the “CAC Articles”), CAC is providing its public shareholders with the opportunity to redeem all or a portion of their CAC Ordinary Shares at a per-share price, payable in cash, equal to the aggregate amount then on deposit in CAC’s trust account as of two business days prior to the consummation of the Business Combination, including interest, less taxes payable, divided by the number of then outstanding CAC Ordinary Shares that were sold as part of the CAC Units in the CAC IPO, subject to the limitations described herein. CAC estimates that the per-share price at which public shares may be redeemed from cash held in the trust account will be approximately $[    ] at the time of the CAC EGM. CAC’s public shareholders may elect to redeem their shares, regardless of whether they are voting for or against such proposed Business Combination or do not vote at all. Under the CAC Articles (and unless the shareholders approve the NTA Proposal), CAC will not redeem Public Shares that would cause CAC’s net tangible assets to be less than US$5,000,001 either immediately prior to, or upon consummation of, or any greater net tangible asset or cash requirement that may be contained in the agreement relating to, such Business Combination, or otherwise CAC is exempt from the provisions of Rule 419 promulgated under the Securities Act of 1933, as amended. Based on the 2,550,149 CAC Public Shares outstanding after the January 16, 2026 redemptions and the corresponding Trust Account balance of $26,487,288, the maximum number of remaining CAC Public Shares that may be redeemed while satisfying the NTA Requirement would be 1,965,140, or approximately 77% of the remaining CAC Public Shares. Any redemptions above that level would cause CAC’s net tangible book value to fall below $5,000,001, absent approval of the NTA Requirement Amendment Proposal or other offsetting adjustments.

Holders of outstanding CAC Rights do not have redemption rights in connection with the Business Combination.

CAC is providing this proxy statement/prospectus and accompanying proxy card to its shareholders in connection with the solicitation of proxies to be voted at the CAC EGM and at any adjournments or postponements of the CAC EGM. The Initial Shareholders, which collectively own approximately [    ]% of CAC Ordinary Shares as of the record date, have agreed to vote their CAC Ordinary Shares in favor of the Business Combination Proposal and the Merger Proposal, which transactions comprise the Business Combination, and intend to vote for the NTA Proposal, the Pubco Equity Plan Proposal, the ESPP Proposal, the Nasdaq Proposal, the Pubco Director Election Proposal, and the Adjournment Proposal, although there is no agreement in place with respect to voting on those proposals.

Each shareholder’s vote is very important. Whether or not you plan to attend the CAC EGM in person by virtual attendance, please submit your proxy card without delay. CAC’s shareholders may revoke proxies at any time before they are voted at the extraordinary general meeting. Voting by proxy will not prevent a shareholder from voting in person by virtual attendance if such shareholder subsequently chooses to attend the CAC EGM.

The CAC Board has approved the Business Combination Agreement, and recommends that CAC shareholders vote “FOR” approval of each of the Proposals. When you consider the recommendation of CAC Board of these Proposals, you should keep in mind that CAC’s directors and officers have interests in the Business Combination that may conflict with or differ from your interests as a shareholder. See the section titled “Proposal No. 2 — The Business Combination Proposal — Interests of the Sponsor and CAC’s Directors and Officers in the Business Combination.”

On behalf of the CAC Board, I thank you for your support and CAC looks forward to the successful consummation of the Business Combination.

This proxy statement/prospectus is dated        , 2026 and is first being mailed to shareholders of CAC on or about        , 2026.

NOTICE OF EXTRAORDINARY GENERAL MEETING OF SHAREHOLDERS
OF COLUMBUS ACQUISITION CORP
To Be Held On [    ], 2026

To the Shareholders of Columbus Acquisition Corp:

NOTICE IS HEREBY GIVEN that an extraordinary general meeting (the “CAC EGM” or “extraordinary general meeting”) of Columbus Acquisition Corp, a Cayman Islands exempted company (“CAC,” “we,” “our,” or “us”), will be held on [    ], 2026 at [    ] a.m., Eastern Time at the offices of Loeb & Loeb LLP, 345 Park Avenue, New York, NY 10154, and virtually via a teleconference using the following dial-in information:

Within the U.S. and Canada Toll Free

Outside of the U.S. and Canada

Participant Passcode

At the extraordinary general meeting, CAC shareholders will be asked to consider and vote upon the following proposals:

•        Proposal No. 1 — The NTA Proposal — to consider and vote upon a proposal to approve, by special resolution, the amendment of the CAC Articles, which currently restricts consummation of a shareholder redemption offer in connection with a business combination if the redemptions made pursuant to such offer would cause CAC to have net tangible assets of less than US$5,000,001 prior to or upon consummation of a business combination (the “NTA Requirement”) as set out in Articles 37.2, 37.5, 37.6 and 37.8 of the CAC Articles, in order to expand the methods that CAC may employ to not become subject to the “penny stock” rules of the SEC, immediately prior to the Effective Time (as defined in the Plan of Merger) (the “NTA Proposal”);

•        Proposal No. 2 — The Business Combination Proposal — to consider and vote upon a proposal to approve and authorize, by ordinary resolution, the Business Combination Agreement, dated as of November 9, 2025 (as amended from time to time), by and among Columbus Acquisition Corp, WISeSat.Space Holdings Corp., a British Virgin Islands business company (“Pubco”), WISeSat Merger Sub Corp., a Cayman Islands exempted company and a wholly owned subsidiary of Pubco (“Merger Sub”), WISeSat.Space Corp., a British Virgin Islands business company (the “Company”), WISeKey International Holding Ltd., a Swiss company (“WISeKey” and together with its successors and permitted assigns, and any holders of Company Ordinary Shares or Company Class F Shares immediately prior to the Effective Time, collectively, the “Seller”), a copy of which is attached to this proxy statement/prospectus as Annex A, and the transactions contemplated therein, which we refer to as the “Business Combination”;

•        Proposal No. 3 — The Merger Proposal — to consider and vote upon a proposal to approve and authorize, by special resolution, that (a) CAC merge with Merger Sub so that Merger Sub will merge with and into CAC and CAC will be the surviving company and all the undertaking, property and liabilities of the Merger Sub vest in CAC by virtue of such merger pursuant to the Companies Act (As Revised); (b) the Plan of Merger substantially in the form annexed to this Proxy Statement as Annex A-1 be and is hereby authorized, approved and confirmed in all respects and CAC be authorized to enter into the Plan of Merger; (c) that upon the Effective Time (as defined in the Plan of Merger): (i) the amending and restating of the memorandum and articles of CAC as the surviving company of the Merger is approved in all respects, (ii) the board of directors and executive officers of CAC resign and the board of directors and the executive officers of Merger Sub immediately prior to the Effective Time become the board of directors and executive officers of the Surviving Company; and (iii) the authorized share capital of CAC (as the surviving company of the Merger) shall be amended such that firstly, all authorized preference shares of par value US$0.0001 each shall be redesignated as authorized ordinary shares of a par value of US$0.0001 each, such that the authorized share capital of CAC (as the surviving company of the Merger) shall be US$50,000 divided into 500,000,000 ordinary shares of a par value of US$0.0001 each (the “Redesignation”); secondly, upon the Redesignation becoming effective, the authorized share capital of CAC (as the surviving company of the Merger) shall be consolidated and divided so as to become US$50,000 divided into 5,000,000 ordinary shares of a par value of $0.01 each (the “Share Consolidation”); and thirdly (iii) upon the Share Consolidation becoming effective, the authorized share capital of CAC (as the surviving company of the Merger) shall be decreased from $50,000 divided into 5,000,000 ordinary shares of a par value of $0.01 each to $1 divided into 100 ordinary shares of a par value of $0.01 each;

•        Proposal No. 4 — The Pubco Equity Plan Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, the adoption of a new equity incentive plan (the “Pubco Equity Plan”) by Pubco (the “Pubco Equity Plan Proposal”). A copy of the Pubco Equity Plan is attached to the accompanying proxy statement/prospectus as Annex D;

•        Proposal No. 5 — The ESPP Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, the adoption of an employee share purchase program (the “Employee Share Purchase Program”) by Pubco (the “ESPP Proposal”). A copy of the Pubco Equity Plan is attached to the accompanying proxy statement/prospectus as Annex E;

•        Proposal No. 6 — The Nasdaq Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, for purposes of complying with applicable listing rules of The Nasdaq Stock Market, the issuance of up to an aggregate of 31,385,052 Pubco Ordinary Shares, no par value, in connection with the Merger and the Share Exchange (the “Nasdaq Proposal”);

•        Proposal No. 7 — The Pubco Director Election Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, that seven directors be elected to serve terms on Pubco’s board of directors effective at the Closing (the “Pubco Director Election Proposal”); and

•        Proposal No. 8 — The Adjournment Proposal — to consider and vote upon a proposal to approve, by ordinary resolution the adjournment of the extraordinary general meeting to a later date or dates, if necessary or appropriate, to permit further solicitation and vote of proxies in the event that there are insufficient votes for, or otherwise in connection with, the NTA Proposal, the Business Combination Proposal, the Merger Proposal, the Pubco Equity Plan Proposal, the ESPP Proposal, the Nasdaq Proposal, or the Pubco Director Election Proposal (the “Adjournment Proposal”).

The Business Combination Proposal is conditioned on the approval of the Merger Proposal, the Pubco Equity Plan Proposal, the ESPP Proposal, the Nasdaq Proposal, and the Pubco Director Election Proposal (collectively, the “Condition Precedent Proposals”). Each of the Merger Proposal, the Pubco Equity Plan Proposal, the ESPP Proposal, the Nasdaq Proposal, and the Pubco Director Election Proposal is conditioned on the approval of the Business Combination Proposal. Therefore, if the Business Combination Proposal is not approved, then the Merger Proposal, the Pubco Equity Plan Proposal, the ESPP Proposal, the Nasdaq Proposal, and the Pubco Director Election Proposal will not be presented to CAC’s shareholders at the CAC EGM. The NTA Proposal and the Adjournment Proposal are not conditioned on the approval of any other Proposal set forth in the accompanying proxy statement/prospectus.

Only holders of record of CAC Ordinary Shares, par value $0.0001 each share, of CAC (the “CAC Ordinary Shares”) at the close of business on [    ] (the “Record Date”) are entitled to notice of the CAC EGM and to vote at the CAC EGM and any adjournments thereof.

CAC is providing the accompanying proxy statement/prospectus and accompanying proxy card to its shareholders in connection with the solicitation of proxies to be voted at the CAC EGM and at any adjournments thereof. Information about the CAC EGM, the Business Combination, and other related business to be considered by CAC’s shareholders at the CAC EGM is included in the accompanying proxy statement/prospectus.

Whether or not you plan to attend the CAC EGM, all of CAC’s shareholders are urged to read the accompanying proxy statement/prospectus, including the annexes and other documents referred to therein, carefully and in their entirety. In particular, you should carefully consider the matters discussed under “Risk Factors” beginning on page 42 of the accompanying proxy statement/prospectus.

Pursuant to the CAC Articles, a holder of CAC Ordinary Shares issued as part of the units sold in CAC’s initial public offering (the “CAC Public Shares” or “Public Shares,” and holders of such Public Shares, the “Public Shareholders”), other than the initial shareholders, may request that CAC redeem all or a portion of its Public Shares for cash if the Business Combination is consummated. As a holder of Public Shares, you will be entitled to receive cash for any Public Shares to be redeemed only if you:

•        hold Public Shares, or if you hold Public Shares through CAC units sold in CAC’s initial public offering (the “CAC Units”), you elect to separate your CAC Units into the underlying Public Shares and CAC Rights prior to exercising your redemption rights with respect to the Public Shares;

•        submit a written request to Continental Stock Transfer & Trust Company, CAC’s transfer agent, in which you (1) request that CAC redeem all or a portion of your Public Shares for cash; (2) identify yourself as the beneficial holder of the Public Shares and provide your legal name phone number, and address; and

•        deliver your Public Shares to Continental Stock Transfer & Trust Company, CAC’s transfer agent, physically or electronically using the Depository Trust Company’s (“DTC”) DWAC (Deposit/Withdrawal At Custodian) System.

Holders must complete the procedures for electing to redeem their Public Shares in the manner described above prior to 5:00 P.M., Eastern time, on [    ], 2026 (two business days before the CAC EGM) in order for their Public Shares to be redeemed.

Holders of CAC Units must elect to separate the CAC Units into the underlying CAC Ordinary Shares and CAC Rights prior to exercising redemption rights with respect to the Public Shares. If Public Shareholders hold their CAC Units in an account at a brokerage firm or bank, such Public Shareholders must notify their broker or bank that they elect to separate the CAC Units into the underlying Public Shares and CAC Rights, or if a holder holds CAC Units registered in its own name, the holder must contact Continental Stock Transfer & Trust Company, CAC’s transfer agent, directly and instruct it to do so. The redemption rights include the requirement that a holder must identify itself to CAC in order to validly redeem its shares. Public Shareholders (other than the initial shareholders) may elect to exercise their redemption rights with respect to their Public Shares even if they vote “FOR” the Business Combination Proposal. If the Business Combination is not consummated, the Public Shares will be returned to the respective holder, broker, or bank. If the Business Combination is consummated, and if a Public Shareholder properly exercises its redemption right with respect to all or a portion of the Public Shares that it holds and timely delivers its shares to Continental Stock Transfer & Trust Company, CAC will redeem the related Public Shares for a per-share price, payable in cash, equal to the aggregate amount then on deposit in the Trust Account, including interest earned on the funds held in the Trust Account and not previously released to CAC, divided by the number of the then-outstanding CAC Public Shares, which redemption will completely extinguish Public Shareholders’ rights as shareholders (including the right to receive further liquidation distributions, if any). For illustrative purposes, as of December 31, 2025, this would have amounted to approximately $10.37 per issued and outstanding Public Share. If a Public Shareholder exercises its redemption rights in full, then it will not own Public Shares or Pubco Ordinary Shares following the redemption. See “Extraordinary General Meeting of CAC Shareholders — Redemption Rights” in the accompanying proxy statement/prospectus for a detailed description of the procedures to be followed if you wish to exercise your redemption rights with respect to your Public Shares.

The approval of each of the Business Combination Proposal, the Pubco Equity Plan Proposal, the ESPP Proposal, the Nasdaq Proposal, the Pubco Director Election Proposal, and the Adjournment Proposal are being proposed as an ordinary resolution, being the affirmative vote (in person or by proxy) of the holders of a majority of the CAC Ordinary Shares entitled to vote and actually casting votes thereon at the CAC EGM. Approval of each of the NTA Proposal and the Merger Proposal requires a special resolution under Cayman Islands law, being the affirmative vote (in person or by proxy) of the holders of at least two-thirds of the CAC Ordinary Shares entitled to vote and actually casting votes thereon at the CAC EGM. Accordingly, a shareholder’s failure to vote in person, online, or by proxy at the CAC EGM will have no effect on the outcome of the vote on any of the Proposals. Abstentions and broker non-votes, while considered present for the purposes of establishing a quorum, will not count as votes cast at the extraordinary general meeting.

YOUR VOTE IS VERY IMPORTANT, REGARDLESS OF THE NUMBER OF CAC ORDINARY SHARES YOU OWN.    To ensure your representation at the CAC EGM, please complete and return the enclosed proxy card or submit your proxy by following the instructions contained in the accompanying proxy statement/prospectus and on your proxy card. Please submit your proxy promptly, whether or not you expect to attend the meeting. If you hold your shares in “street name,” you should instruct your broker, bank, or other nominee how to vote in accordance with the voting instruction form you received from your broker, bank, or other nominee.

MARKET AND INDUSTRY DATA

Certain information contained in this document relates to or is based on studies, publications, surveys and other data obtained from publicly available third-party sources and CAC’s and the Company’s own internal estimates and research. While we believe these third-party sources to be reliable as of the date of this proxy statement/prospectus, we have not independently verified the market and industry data contained in this proxy statement/prospectus or the underlying assumptions relied on therein. Finally, while we believe our own internal research is reliable, such research has not been verified by any independent source.

TRADEMARKS

This document contains references to trademarks, trade names and service marks belonging to other entities. Solely for convenience, trademarks, trade names and service marks referred to in this proxy statement/prospectus may appear without the ® or ™ symbols, but such references are not intended to indicate, in any way, that the applicable licensor will not assert, to the fullest extent under applicable law, its rights to these trademarks and trade names. We do not intend our use or display of other companies’ trade names, trademarks or service marks to imply a relationship with, or endorsement or sponsorship of us by, any other companies.

TABLE OF CONTENTS

ABOUT THIS PROXY STATEMENT/PROSPECTUS

This proxy statement/prospectus, which forms a part of a registration statement on Form F-4 filed with the SEC by Pubco, constitutes a prospectus of Pubco under Section 5 of the Securities Act with respect to (1) the Pubco Ordinary Shares to be issued to CAC shareholders and (2) the Pubco Ordinary Shares to be issued to shareholders of the Company, including Company Ordinary Shares and Company Class F Shares, and including Seller and its successors and permitted assigns, in each case in connection with the Business Combination Agreement. This document also constitutes a proxy statement of CAC under Section 14(a) of the Exchange Act, and the rules thereunder, and a notice of meeting with respect to the extraordinary general meeting of CAC shareholders to consider and vote upon the NTA Proposal, the Business Combination Proposal, the Merger Proposal, the Pubco Equity Plan Proposal, the ESPP Proposal, the Nasdaq Proposal, the Pubco Director Election Proposal, and the Adjournment Proposal.

Unless otherwise indicated or the context otherwise requires, all references in this proxy statement/prospectus to the terms “Pubco” refer to WISeSat.Space Holdings Corp. All references in this proxy statement/prospectus to “CAC” refer to Columbus Acquisition Corp. All references in this proxy statement/prospectus to the “Company” refer to WISeSat.Space Corp. and its subsidiaries, including WISeSat.Space AG, a Swiss company (which is referred to as “WISeSat Opco”).

This proxy statement/prospectus does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy, in any jurisdiction to or from any person to whom it is not lawful to make any such offer or solicitation in such jurisdiction.

ADDITIONAL INFORMATION

No person is authorized to give any information or to make any representation with respect to the matters that the accompanying proxy statement/prospectus describes other than those contained in the accompanying proxy statement/prospectus, and, if given or made, the information or representation must not be relied upon as having been authorized by the Company, CAC or WISeKey. The accompanying proxy statement/prospectus does not constitute an offer to sell or a solicitation of an offer to buy securities or a solicitation of a proxy in any jurisdiction where, or to any person to whom, it is unlawful to make such an offer or a solicitation. Neither the delivery of the accompanying proxy statement/prospectus nor any distribution of securities made under the accompanying proxy statement/prospectus will, under any circumstances, create an implication that there has been no change in the affairs of the Company, CAC or the Company since the date of the accompanying proxy statement/prospectus or that any information contained therein is correct as of any time subsequent to such date.

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This proxy statement/prospectus contains forward-looking statements that involve substantial risks and uncertainties. All statements other than statements of historical facts contained in this proxy statement/prospectus, including statements regarding CAC’s, the Company’s or Pubco’s future financial position, business strategy and plans and objectives of management for future operations, are forward-looking statements. In some cases, you can identify forward-looking statements by terminology such as “may,” “will,” “should,” “expects,” “plans,” “anticipates,” “could,” “intends,” “targets,” “projects,” “contemplates,” “believes,” “estimates,” “predicts,” “potential” or “continue” or the negative of these terms or other similar expressions. Forward-looking statements include, without limitation, Pubco’s, the Company’s or CAC’s expectations concerning the outlook for their business, productivity, plans and goals for future operational improvements and capital investments, operational performance, future market conditions or economic performance and developments in the capital and credit markets and expected future financial performance, as well as any information concerning possible or assumed future results of operations of Pubco as set forth in the sections of this proxy statement/prospectus titled “Proposal No. 2 — The Business Combination Proposal — CAC Board’s Reasons for the Approval of the Business Combination.” Forward-looking statements also include statements regarding the expected benefits of the proposed Business Combination between Pubco, the Seller and CAC.

Forward-looking statements involve a number of risks, uncertainties and assumptions, and actual results or events may differ materially from those projected or implied in those statements. Important factors that could cause such differences include, but are not limited to:

•        the occurrence of any event, change or other circumstances that could delay the Business Combination or give rise to the termination of the Business Combination Agreement;

•        the outcome of any legal proceedings that have been or may be instituted against CAC, Pubco, or the Company following announcement of the Business Combination;

•        the inability to complete the Business Combination due to the failure to obtain approval of the shareholders of CAC, or satisfy the other conditions to closing in the Business Combination Agreement;

•        the ability to obtain or maintain the listing of Pubco Ordinary Shares on Nasdaq following the Business Combination;

•        the risk that the proposed Business Combination disrupts current plans and operations of the Company or CAC as a result of the announcement and consummation of the Business Combination;

•        CAC’s ability to realize the anticipated benefits of the Business Combination, which may be affected by, among other things, competition and the ability of Pubco to grow and manage growth profitably following the Business Combination;

•        costs related to the Business Combination;

•        Pubco’s markets are rapidly evolving and may decline or experience limited growth;

•        Pubco’s ability to retain and expand its customer base;

•        Pubco’s ability to compete effectively in the markets in which it operates;

•        failure to prevent security breaches or unauthorized access to Pubco’s or its third-party service providers’ information technologies systems;

•        changes in applicable laws, rules, regulations and industry standards;

•        risks related to Pubco’s corporate structure;

•        global economic and geopolitical development; and

•        the other matters described in the section titled “Risk Factors” beginning on page 42.

In addition, the Business Combination is subject to the satisfaction of the conditions to the completion of the Business Combination set forth in the Business Combination Agreement and the absence of events that could give rise to the termination of the Business Combination Agreement, the possibility that the Business Combination does not close, and risks that the proposed Business Combination disrupts current plans and operations and business relationships, or poses difficulties in attracting or retaining employees for Pubco.

Pubco, CAC and the Company caution you against placing undue reliance on forward-looking statements, which reflect current beliefs and are based on information currently available as of the date a forward-looking statement is made. Forward-looking statements set forth herein speak only as of the date of this proxy statement/prospectus. None of Pubco, CAC and the Company undertakes any obligation to revise forward-looking statements to reflect future events, changes in circumstances, or changes in beliefs. In the event that any forward-looking statement is updated, no inference should be made that Pubco, CAC and the Company will make additional updates with respect to that statement, related matters, or any other forward-looking statements. Any corrections or revisions and other important assumptions and factors that could cause actual results to differ materially from forward-looking statements, including discussions of significant risk factors, may appear, up to the consummation of the Business Combination, in CAC’s public filings with the SEC or, upon and following the consummation of the Business Combination, in Pubco’s public filings with the SEC, which are or will be (as appropriate) accessible at www.sec.gov, and which you are advised to consult. For additional information, please see the section titled “Where You Can Find More Information” on page 219.

Market, ranking and industry data used throughout this proxy statement/prospectus, including statements regarding market size, is based on independent industry surveys and publications and other data obtained from third-party sources. These data involve a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. While we are not aware of any misstatements regarding the industry data presented herein, its estimates involve risks and uncertainties and are subject to change based on various factors, including those discussed under the headings “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations of the Company.” in this proxy statement/prospectus.

PRESENTATION OF FINANCIAL AND OTHER INFORMATION

Financial Statements

The historical financial statements of CAC included in this proxy statement/prospectus have been prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) and are denominated in U.S. dollars. The historical financial statements of Pubco included in this proxy statement/prospectus have been prepared in accordance with U.S. GAAP and are denominated in U.S. dollars. The historical financial statements of the Company and WISeSat Opco included in this proxy statement/prospectus have been prepared in accordance with U.S. GAAP and are denominated in U.S. dollars.

FREQUENTLY USED TERMS

In this document, unless the context otherwise requires:

“Business Combination” means the Share Exchange together with the Merger and all other transactions contemplated by the Business Combination Agreement and the Ancillary Documents.

“Business Combination Agreement” means the certain Business Combination Agreement, dated as of November 9, 2025, by and among CAC, Pubco, Merger Sub, WISeKey, and the Company.

“BVI” means the British Virgin Islands.

“BVI Companies Act” means the BVI Business Companies Act, amended and restated memorandum and articles 2020.

“BVI Insolvency Act” means the Insolvency Act, (Revised 2020) of the British Virgin Islands, as amended.

“CAC Articles” means the First Amended and Restated Memorandum and Articles of Association; provided, that references herein to the CAC Charter for periods after the Effective Time includes the amended and restated memorandum and articles of association of the Surviving Company.

“CAC Board” means the Board of Directors of CAC.

“CAC IPO” means the initial public offering of CAC, which was consummated on January 24, 2025.

“CAC IPO Underwriter” means A.G.P./Alliance Global Partners.

“CAC Ordinary Shares” means ordinary shares of CAC, par value $0.0001 per share.

“CAC Public Rights” means the issued and outstanding rights of CAC sold in the CAC IPO as part of CAC Units, each such right convertible into one-seventh (1/7) of a CAC Ordinary Share at the closing of a business combination.

“CAC Public Shares” means the shares of CAC Ordinary Shares sold in the CAC IPO.

“CAC Rights” means the issued and outstanding rights of CAC, each such right convertible into one-seventh (1/7) of a CAC Ordinary Share at the closing of a business combination.

“CAC Units” means a unit of CAC issued in the CAC IPO, comprising of one CAC Ordinary Share and one CAC Right.

“Company” means WISeSat.Space Corp., a British Virgin Islands business company and its subsidiaries, including WISeSat.Space AG, a Swiss company.

“Cayman Companies Act” means the Companies Act (As Revised) of the Cayman Islands.

“Code” means the U.S. Internal Revenue Code of 1986, as amended.

“Company Class F Shares” means the Class F ordinary shares, no par value, of the Company, which Company Class F Shares in the aggregate are entitled to 49.99% of the total vote on any matter voted on by the holders Company Shares and which Company Class F Shares will automatically convert into Company Ordinary Shares upon certain transfers in accordance with the Company Organizational Documents.

“Company Ordinary Shares” means the ordinary shares, no par value, of the Company, each of which is entitled to one (1) vote per share.

“Effective Time” means the time that the Merger becomes effective, which shall occur at the time on the Closing Date when the Plan of Merger is registered by the Registrar or at such other time as may be agreed in writing by the Company and CAC and specified in the Plan of Merger, provided that such date shall not be a date later than the ninetieth day following the date of such registration.

“Exchange Act” means the U.S. Securities Exchange Act of 1934, as amended.

“Founder Shares” means the CAC Ordinary Shares initially purchased by the Sponsor in a private placement prior to the CAC IPO and, unless context otherwise requires, the term also includes CAC’s ordinary shares issued upon the conversion thereof.

“Initial Shareholders” means the holders of our Founder Shares sold prior to this offering, including CAC, the Sponsor, CAC IPO Underwriter and the former and current independent directors of CAC.

“Investment Company Act” means the U.S. Investment Company Act of 1940, as amended.

“IRS” means U.S. Internal Revenue Service.

“JOBS Act” means the U.S. Jumpstart Our Business Startups Act of 2012, as amended.

“Merger” means the merger of Merger Sub with and into CAC, with CAC surviving the merger as a wholly owned subsidiary of Pubco.

“Merger Sub” means WISeSat Merger Sub Corp., a Cayman Islands exempted company and a wholly owned subsidiary of Pubco.

“Nasdaq” means the Nasdaq Stock Market LLC, and includes either the Nasdaq Global Market or the Nasdaq Capital Market, as applicable to the relevant listing.

“Nasdaq Listing Rules” means the Listing Rules adopted by Nasdaq, as the same may be amended from time to time.

“PCAOB” means the U.S. Public Company Accounting Oversight Board.

“PFIC” means passive foreign investment company.

“Private Placement” means the private placement of 234,290 Private Placement Units purchased by the Sponsor, which was consummated simultaneously with the completion of the initial public offering, at a purchase price of $10.00 per unit for a total purchase price of approximately $2,342,900.

“Private Placement Rights” means the rights to purchase an aggregate of 33,470 CAC Ordinary Shares comprising the Placement Units purchased separately by the Sponsor in the Private Placement.

“Private Placement Units” means the 234,290 Units purchased separately by the Sponsor in the Private Placement, each Placement Unit consisting of one Private Placement Share and one Private Placement Right.

“Pubco” means WISeSat.Space Holdings Corp., a British Virgin Islands business company.

“Pubco Ordinary Shares” means ordinary shares, no par value, of Pubco, each of which is entitled to one vote per share.

“Pubco Class F Shares” means class F ordinary shares, no par value, of Pubco, which Pubco Class F Shares in the aggregate are entitled to 49.99% of the total vote on any matter voted on by the holders Pubco Shares and which Pubco Class F Shares are convertible by the holder thereof on a one for one basis into Pubco Ordinary Shares and will automatically convert into Pubco Ordinary Shares upon a change of control of a holder of Pubco Class F Shares in accordance with the Restated Pubco Charter.

“Pubco Shares” means, collectively, Pubco Ordinary Shares and Pubco Class F Shares.

“Redemption Rights” means the right of each CAC Public Shareholder to redeem all or a portion of their CAC Public Shares in accordance with the amended and restated memorandum and articles of association of CAC.

“Representative Shares” means 210,000 CAC Ordinary Shares issued to A.G.P./Alliance Global Partners and/or its designees at the CAC IPO.

“Restated Pubco Charter” means Pubco’s amended memorandum and articles of incorporation, to be effective upon completion of the Business Combination, a copy of which is appended to this proxy statement/prospectus as Annex C.

“SEC” means the U.S. Securities and Exchange Commission.

“Securities Act” means the U.S. Securities Act of 1933, as amended.

“SEALSQ” means SEALSQ Corp (Nasdaq: LAES), a subsidiary of WISeKey.

“Seller” means WISeKey International Holding Ltd. (SIX: WIHN, NASDAQ: WKEY), a Swiss stock corporation (Aktiengesellschaft) of unlimited duration with limited liability under the laws of Switzerland and registered in the Commercial Register of the Canton of Zug, Switzerland, on December 2, 2015 (together with its successors, including after its anticipated domestication to the British Virgin Islands prior to the Closing); as well as any other holder(s) of Company Ordinary Shares or Company Class F Shares immediately prior to the Effective Time.

“Share Exchange” means that Pubco will acquire all of the issued and outstanding Company Ordinary Shares and Company Class F Shares from the Seller in exchange for Pubco Ordinary Shares and Pubco Class F Shares, with the Company becoming a wholly owned subsidiary of Pubco and the Seller becoming a shareholder of Pubco.

“Sponsor” means Hercules Capital Management VII Corp, a British Virgin Islands business company controlled by Dr. Fen “Eric” Zhang, CEO of CAC.

“Tax Act” means the U.S. Tax Cuts and Jobs Act of 2017.

“Transactions” means the Business Combination.

“Trust Account” means the trust account established by CAC with the proceeds from the CAC IPO pursuant to an Investment Management Trust Agreement by and between CAC and the Trustee, dated January 22, 2025, as amended on January 16, 2026.

“Trustee” means Continental Stock Transfer & Trust Company, LLC.

“U.S. GAAP” or “GAAP” means United States generally accepted accounting principles.

“$” means United States dollars, the lawful currency of the United States of America.

QUESTIONS AND ANSWERS ABOUT THE BUSINESS COMBINATION AND THE EXTRAORDINARY GENERAL MEETING

The following questions and answers briefly address some commonly asked questions about the proposals to be presented at the CAC EGM, including with respect to the proposed Transactions. The following questions and answers do not include all of the information that may be important to CAC’s shareholders. CAC shareholders are urged to carefully read this entire proxy statement/prospectus, including the annexes and the other documents referred to herein, to fully understand the proposed Transactions and the voting procedures for the CAC EGM.

Q:     Why am I receiving this proxy statement/prospectus?

A:     CAC shareholders are being asked to consider and vote upon a proposal to approve and adopt the Business Combination and certain related proposals. CAC, Pubco and other parties have agreed to the Business Combination under the terms of the Business Combination Agreement that is described in this proxy statement/prospectus. The Business Combination Agreement provides for, among other things, that on the Closing Date, Merger Sub will merge with and into CAC with CAC continuing as the surviving company of the Merger and as a wholly owned subsidiary of Pubco, WISeSat.Space Holdings Corp. This proxy statement/prospectus and its annexes contain important information about the proposed Business Combination and the other matters to be acted upon at the CAC EGM. You should read this proxy statement/prospectus and its annexes carefully and in their entirety.

Q:     When and where is the Meeting?

A:     The CAC EGM will take place at [    ] on [    ], 2026, and virtually in a virtual meeting format using the following dial-in information. Shareholders are encouraged to attend the CAC EGM virtually:

This proxy statement includes instructions on how to access the virtual extraordinary general meeting and how to listen and vote from home or any remote location with Internet connectivity.

Q:     What is being voted on at the CAC EGM?

A:     CAC shareholders will vote on the following proposals at the CAC EGM:

•        Proposal No. 1 — The NTA Proposal — to consider and vote upon a proposal to approve, by special resolution, the amendment of the CAC Articles, which currently restricts consummation of a shareholder redemption offer in connection with a business combination if the redemptions made pursuant to such offer would cause CAC to have net tangible assets of less than US$5,000,001 prior to or upon consummation of a business combination (the “NTA Requirement”) as set out in Articles 37.2, 37.5, 37.6 and 37.8 of the CAC Articles, in order to expand the methods that CAC may employ to not become subject to the “penny stock” rules of the SEC, immediately prior to the Effective Time (as defined in the Plan of Merger) (the “NTA Proposal”);

•        Proposal No. 2 — The Business Combination Proposal — to consider and vote upon a proposal to approve and authorize, by ordinary resolution, the Business Combination Agreement, dated as of November 9, 2025 (as amended from time to time), by and among Columbus Acquisition Corp, WISeSat.Space Holdings Corp., a British Virgin Islands business company (“Pubco”), WISeSat Merger Sub Corp., a Cayman Islands exempted company and a wholly owned subsidiary of Pubco (“Merger Sub”), WISeSat.Space Corp., a British Virgin Islands business company (the “Company”), WISeKey International Holding Ltd., a Swiss company (“WISeKey” and together with its successors and permitted assigns, and any holders of Company Ordinary Shares or Company Class F Shares immediately prior to the Effective Time, collectively, the “Seller”), a copy of which is attached to this proxy statement/prospectus as Annex A, and the transactions contemplated therein, which we refer to as the “Business Combination”;

•        Proposal No. 3 — The Merger Proposal — to consider and vote upon a proposal to approve and authorize, by special resolution, that (a) CAC merge with Merger Sub so that Merger Sub will merge with and into CAC and CAC will be the surviving company and all the undertaking, property and liabilities of the Merger Sub vest in CAC by virtue of such merger pursuant to the Companies Act (As Revised); (b) the Plan of Merger substantially in the form annexed to this Proxy Statement as Annex A-1 be and is hereby authorized, approved and confirmed in all respects and CAC be authorized to enter into the Plan of Merger; (c) that upon the Effective Time (as defined in the Plan of Merger): (i) the amending and restating of the memorandum and articles of CAC as the surviving company of the Merger is approved in all respects, (ii) the board of directors and executive officers of CAC resign and the board of directors and the executive officers of Merger Sub immediately prior to the Effective Time become the board of directors and executive officers of the Surviving Company; and (iii) the authorized share capital of CAC (as the surviving company of the Merger) shall be amended such that firstly, all authorized preference shares of par value US$0.0001 each shall be redesignated as authorized ordinary shares of a par value of US$0.0001 each, such that the authorized share capital of CAC (as the surviving company of the Merger) shall be US$50,000 divided into 500,000,000 ordinary shares of a par value of US$0.0001 each (the “Redesignation”); secondly, upon the Redesignation becoming effective, the authorized share capital of CAC (as the surviving company of the Merger) shall be consolidated and divided so as to become US$50,000 divided into 5,000,000 ordinary shares of a par value of $0.01 each (the “Share Consolidation”); and thirdly (iii) upon the Share Consolidation becoming effective, the authorized share capital of CAC (as the surviving company of the Merger) shall be decreased from $50,000 divided into 5,000,000 ordinary shares of a par value of $0.01 each to $1 divided into 100 ordinary shares of a par value of $0.01 each;

•        Proposal No. 4 — The Pubco Equity Plan Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, the adoption of a new equity incentive plan (the “Pubco Equity Plan”) by Pubco (the “Pubco Equity Plan Proposal”). A copy of the Pubco Equity Plan is attached to the accompanying proxy statement/prospectus as Annex D;

•        Proposal No. 5 — The ESPP Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, the adoption of an employee share purchase program (the “Employee Share Purchase Program”) by Pubco (the “ESPP Proposal”). A copy of the Pubco Equity Plan is attached to the accompanying proxy statement/prospectus as Annex E;

•        Proposal No. 6 — The Nasdaq Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, for purposes of complying with applicable listing rules of The Nasdaq Stock Market, the issuance of up to an aggregate of 31,385,052 Pubco Ordinary Shares, no par value, in connection with the Merger and the Share Exchange (the “Nasdaq Proposal”);

•        Proposal No. 7 — The Pubco Director Election Proposal — to consider and vote upon a proposal to approve, by ordinary resolution, that seven directors be elected to serve terms on Pubco’s board of directors effective at the Closing (the “Pubco Director Election Proposal”); and

•        Proposal No. 8 — The Adjournment Proposal — to consider and vote upon a proposal to approve, by ordinary resolution the adjournment of the extraordinary general meeting to a later date or dates, if necessary or appropriate, to permit further solicitation and vote of proxies in the event that there are insufficient votes for, or otherwise in connection with, the NTA Proposal, the Business Combination Proposal, the Merger Proposal, the Pubco Equity Plan Proposal, the ESPP Proposal, the Nasdaq Proposal, or the Pubco Director Election Proposal (the “Adjournment Proposal”).

Q:     Are the Proposals conditioned on one another?

A:     CAC may not consummate the Business Combination unless the Condition Precedent Proposals are approved at the CAC EGM. Each of the Condition Precedent Proposals is cross-conditioned on the approval and adoption of each of the other Condition Precedent Proposals. The NTA Proposal and the Adjournment Proposal are not conditioned on the approval of any other Proposal set forth in this proxy statement/prospectus.

Q:     What will happen in the Business Combination?

A:     If the transactions contemplated by the Business Combination Agreement are consummated, (a) Pubco will acquire all of the issued and outstanding Company Ordinary Shares and Company Class F Shares from the Seller in exchange for Pubco Ordinary Shares and Pubco Class F Shares, with the Company becoming a wholly owned subsidiary of Pubco and the Seller becoming a shareholder of Pubco; and (b) Merger Sub will merge with and into CAC, with CAC surviving the Merger as a wholly owned subsidiary of Pubco, as a result of which, (i) CAC shall become a wholly owned Subsidiary of Pubco; and (ii) each issued and outstanding CAC Security immediately prior to the effective time of the Merger shall no longer be outstanding and shall automatically be cancelled, in exchange for the right of the holder thereof to receive Pubco Ordinary Shares, all upon the terms and subject to the conditions set forth in the Business Combination Agreement, the Plan of Merger and in accordance with the Companies Act (As Revised) of the Cayman Islands. At the Effective Time, each CAC Ordinary Share that is issued and outstanding and held by the Public Shareholders (including each CAC Ordinary Share converted from CAC Rights and each CAC Ordinary Share held as a result of the Unit Separation, other than the Excluded Shares, the Dissenting Shares and the Redeemed Shares (each as defined in the Business Combination Agreement)) shall be become and be converted automatically into the right to receive one (1) Pubco Ordinary Share. As a result of the Merger, the separate corporate existence of Merger Sub will cease and CAC will continue as the surviving company of the Merger under the Companies Act. Following the Merger, the shares of the Surviving Company will be directly and solely held by Pubco, and the Surviving Company will become a direct wholly owned subsidiary of Pubco.

For more information on the Merger, see the section in this proxy statement/prospectus entitled “Proposal No. 2 — The Business Combination Proposal.”

Q:     Why is CAC proposing the Business Combination?

A:     CAC was formed for the purpose of effecting a merger, amalgamation, share exchange, asset acquisition, share purchase, reorganization, or similar business combination with one or more businesses or entities. The CAC Board considered a wide variety of factors in connection with its evaluation of the Business Combination, including its review of the results of the due diligence conducted by CAC’s management and CAC’s advisors and the Fairness Opinion from Newbridge. As a result, the CAC Board concluded that a transaction with Pubco would present the most attractive opportunity to maximize value for CAC’s shareholders. Please see “Proposal No. 2 — The Business Combination Proposal — CAC Board’s Reasons for the Approval of the Business Combination.”

Q:     Did the CAC Board obtain a third-party valuation or fairness opinion in determining whether or not to proceed with the Business Combination?

A:     Yes, the CAC Board received a fairness opinion from Newbridge, concluding that, as of the date of such Fairness Opinion, the consideration to be issued, paid or exchanged to shareholders of CAC in the Business Combination is fair from a financial point of view to the shareholders of CAC and the Business Combination is fair from a financial point of view to the securityholders of CAC that are unaffiliated with Sponsor. For additional information, please see “Proposal No. 2 — The Business Combination Proposal — Fairness Opinion of Newbridge” and the opinion of Newbridge attached hereto as Annex B for additional information.

Q:     How will Pubco be managed and governed following the Business Combination?

A:     As of the Closing, the Pubco Board will consist of seven directors, including [      ] independent directors. See “Management of Pubco after the Transactions” for details of the composition of post-closing Pubco Board.

Q:     What equity stake will CAC’s current shareholders and the holders of the CAC Founder Shares hold in Pubco following the consummation of the Business Combination assuming no redemptions?

A:     It is anticipated that, upon completion of the Business Combination, assuming no redemptions, the ownership of Pubco will be as follows:

•        the existing shareholders of the Seller will own 12,352,600 Pubco Ordinary Shares and 12,997,400 Pubco Class F Shares, or approximately 81% of the total issued and outstanding Pubco Shares and 84% of the total voting power;

•        the Public Shareholders will own 3,407,292 Pubco Ordinary Shares, or approximately 11% of the total issued and outstanding Pubco Shares and 9% of the total voting power;

•        the Sponsor will own 1,731,760 Pubco Ordinary Shares, or approximately 6% of the total issued and outstanding Pubco Shares and 5% of the total voting power;

•        A.G.P./Alliance Global Partners will own 210,000 Pubco Ordinary Shares, or approximately 1% of the total issued and outstanding Pubco Shares and 1% of the total voting power; and

•        the one former and two current independent directors of CAC will collectively own 36,000 Pubco Ordinary Shares, or approximately 0% of the total issued and outstanding Pubco Shares and 0% of the total voting power.

See the “Summary Unaudited Pro Forma Condensed Combined Financial Information” for further information.

Q:     How will the Merger affect my CAC Ordinary Shares?

A:     At the Effective Time, pursuant to the Merger, each then-outstanding CAC Ordinary Share (including each CAC Ordinary Share converted from CAC Rights) will be canceled and converted, on a one-for-one basis, into one Pubco Ordinary Share.

Q:     What are the U.S. federal income tax consequences of the Business Combination?

A:     Subject to the assumptions, limitations and qualifications described in “Certain Tax Considerations — Certain Material U.S. Federal Income Tax Considerations,” the Share Exchange and the Merger should be treated as integrated transactions and should qualify as exchanges of property for stock described in Section 351(a) of the Code. If so treated, subject to certain exceptions discussed below, a U.S. Holder would not recognize gain or loss on the exchange of CAC Ordinary Shares for Pubco Ordinary Shares pursuant to the Business Combination. However, there are significant factual and legal uncertainties as to whether the Merger will qualify as an exchange as described in Section 351(a) of the Code, and any change that is made after the date hereof, including any inaccuracy of the facts or assumptions upon which such expectations were based, could adversely affect the intended tax.

Neither CAC nor Pubco intends to request a ruling from the IRS regarding the U.S. federal income tax treatment of the Business Combination, and no assurance can be given that Business Combination will qualify for the intended tax treatment described above, or that the IRS will not challenge this position and that a court will not sustain such a challenge by the IRS. Further, the Closing is not conditioned upon the receipt of an opinion of counsel that the Share Exchange and the Merger will qualify for the intended tax treatment described above.

If the Merger does not qualify as an exchange described in Section 351(a) of the Code, unless the Merger qualifies for nonrecognition treatment under another provision of the Code, then a U.S. Holder that exchanges its CAC Ordinary Shares for the consideration pursuant to the Merger will recognize gain or loss equal to the difference between (i) the fair market value of the Pubco Ordinary Shares received and (ii) the U.S. Holder’s adjusted tax basis in the CAC Ordinary Shares exchanged therefor.

The rules governing the U.S. federal income tax treatment of the Business Combination are complex and will depend on a holder’s particular circumstances. All holders of CAC Securities are urged to consult with their tax advisors regarding the potential tax consequences to them of the Share Exchange and the Merger and the tax consequences if the Share Exchange and the Merger were to fail to qualify for such intended tax treatment described above. For a more complete discussion of the U.S. federal income tax considerations of the Share Exchange and the Merger, see the discussion below under “Certain Tax Considerations — Certain Material U.S. Federal Income Tax Considerations.”

Q:     What interests do CAC’s Directors and Officers have in the Business Combination?

A:     The Sponsor and CAC’s current officers and directors have interests in the Business Combination that are different from or in addition to (and which may conflict with) your interests. You should take these interests into account in deciding whether to approve the Business Combination Proposal. These interests include:

•        the fact that the Sponsor paid an aggregate of $25,000 for 1,725,000 CAC Ordinary Shares, which will have a significantly higher value at the time of the Business Combination but will become worthless if a business combination is not consummated by January 22, 2027 (if CAC extends the period in full, as

further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles). Based on the closing price for the Public Shares of $        on Nasdaq on        , 2026, the value of the Founder Shares held by the Sponsor would be $        ;

•        the fact that the Sponsor paid an aggregate of approximately $2,342,900 for their 234,290 CAC Private Placement Units and that the CAC Private Placement Rights underlying such units will expire worthless if a business combination is not consummated by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles);

•        the fact that the Sponsor is anticipated to hold 6% of issued and outstanding shares of Pubco immediately following the Business Combination (assuming no redemptions of CAC shareholders);

•        the fact that one of the former and two current independent directors of CAC paid an aggregate of $522 for 36,000 CAC Ordinary Shares, which have a significantly higher value at the time of the Business Combination but will become worthless if a business combination is not consummated by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles);

•        the fact that the remaining independent director of CAC held a share purchase option to acquire 12,000 CAC Ordinary Shares from the Sponsor upon the existing lock-up term on such Founder Shares expires, with an initial exercise price of $0.0145 per Ordinary Share, which have a significantly higher value at the time of the Business Combination but will become worthless if a business combination is not consummated by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles);

•        the fact that, given the differential in the purchase price that the Sponsor paid for the Founder Shares and the purchase price that the Sponsor paid for the CAC Private Placement Units as compared to the price of the CAC public shares and CAC Units and the substantial number of CAC Ordinary Shares that the Sponsor will receive upon conversion of the Founder Shares and (as applicable) CAC Private Placement Rights and CAC Ordinary Shares underlying the CAC Private Placement Units, the Sponsor can earn a positive return on their investment, even if CAC public shareholders have a negative return on their investment;

•        the fact that the Sponsor and officers and directors of CAC have agreed not to redeem any CAC Ordinary Shares held by them in connection with the shareholder vote to approve a proposed initial business combination pursuant to a letter agreement entered into with CAC;

•        the fact that CAC’s Sponsor will lose their entire investment if an initial business combination is not consummated by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles);

•        the fact that the Sponsor and officers and directors of CAC have agreed to waive their rights to liquidating distributions from the Trust Account with respect to Founder Shares held by them if CAC fails to complete an initial business combination by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles);

•        the fact that CAC’s Sponsor, officers, directors and their respective affiliates are entitled to reimbursement of reasonable out-of-pocket expenses incurred by them in connection with certain activities on CAC’s behalf, such as identifying and investing possible business targets and business combinations. However, if CAC fails to consummate a business combination within the required period, they will not have any claim against the Trust Account for reimbursement. Accordingly, CAC may not be able to reimburse these expenses if the Business Combination or another business combination is not consummated by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles);

•        the right of CAC’s Sponsor, officers and directors to transfer the Pubco Ordinary Shares held by them following the Business Combination, subject to certain lock-up periods;

•        the fact that CAC’s Sponsor, officers, directors, or their affiliates may, but are not obligated to, provide Working Capital Loans to fund working capital deficiencies or finance transaction costs in connection with an initial business combination. Up to $3,000,000 of such Working Capital Loans may be convertible into units, at a price of $10.00 per unit at the option of the lender, upon consummation of its initial Business Combination.

•        in the event of the liquidation of the Trust Account upon the failure of CAC to consummate a business combination by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles), the Sponsor has agreed to indemnify CAC to ensure that the proceeds in the Trust Account is not reduced below the lesser of (i) $10.00 per public share and (ii) the actual amount per public share held in the trust account as of the date of the liquidation of the trust account, if less than $10.00 per share due to reductions in the value of the trust assets, less taxes payable, provided that such liability will not apply to any claims by a third party or prospective target business who executed a waiver of any and all rights to the monies held in the trust account (whether or not such waiver is enforceable) nor will it apply to any claims under our indemnity of the underwriters of this offering against certain liabilities, including liabilities under the Securities Act;

•        the Sponsor (including their representatives and affiliates) and CAC’s officers and directors are, or in the future may become, affiliated with entities that are engaged in similar business to CAC. The Sponsor and officers and directors of CAC are not prohibited from sponsoring, or otherwise becoming involved with, another blank check company prior to CAC completing its initial business combination. CAC’s officers and directors may become aware of business opportunities which may be appropriate for presentation to CAC, and the other entities to which they owe certain fiduciary or contractual duties. Accordingly, they may have had conflicts of interest in determining to which entity a particular business opportunity should be presented. These conflicts may not be resolved in CAC’s favor and such potential business opportunities may be presented to other entities prior to their presentation to CAC, subject always to applicable fiduciary duties under Cayman Islands law. CAC renounces any interest or expectancy in, or in being offered an opportunity to participate in, any potential transaction or matter which may be a corporate opportunity for any director or officer, on the one hand, and CAC, on the other. CAC does not believe that the fiduciary duties or contractual obligations of its officers or directors will materially affect CAC’s ability to complete the initial business combination;

•        the fact that CAC’s officers and directors have not received any cash compensation;

•        the fact that the Business Combination Agreement provides for the continued indemnification of CAC’s current directors and officers and the continuation of our directors’ and officers’ liability insurance after the Business Combination covering CAC’s current directors and officers;

•        the fact that CAC, the Sponsor, Pubco and certain other holders will enter into an amendment to the Founder Registration Rights Agreement on the Closing which provides for registration rights following consummation of the Business Combination; and

•        the fact that pursuant to the Business Combination Agreement, the Sponsor may make Working Capital Loans, including in connection with the Extension Payments, which will be repaid in cash or converted into CAC Working Capital Units.

Q:     What happens if I sell my CAC Ordinary Shares before the CAC EGM?

A:     The record date for the CAC EGM is earlier than the date that the Business Combination is expected to be completed. If you transfer your CAC Ordinary Shares after the Record Date, but before the CAC EGM, unless the transferee obtains from you a proxy to vote those shares, you will retain your right to vote at the CAC EGM. However, you will not be able to seek redemption of your CAC Ordinary Shares because you will no longer be able to deliver them for cancellation upon consummation of the Business Combination in accordance with the provisions described in this proxy statement/prospectus. If you transfer your CAC Ordinary Shares prior to the Record Date, you will have no right to vote those shares at the CAC EGM or seek redemption of those shares.

Q:     How has the announcement of the Business Combination affected the trading price of the CAC Units, CAC Ordinary Shares and CAC Public Rights?

A:     On November 7, 2025, the trading date before the public announcement of the Business Combination, the CAC Units, CAC Ordinary Shares and CAC Public Rights closed at $10.65, $10.27 and $0.19, respectively. On        , the trading date immediately prior to the date of this proxy statement/prospectus, the CAC Units, CAC Ordinary Shares and CAC Public Rights closed at $        , $         and $        , respectively.

Q:     Following the Business Combination, will CAC’s securities continue to trade on a stock exchange?

A:     The parties and Pubco intend to apply to the Nasdaq that, in connection with the Business Combination, Pubco Ordinary Shares will be listed on Nasdaq under the symbol “WSAT”, which symbol has been reserved by Pubco. As a result of the Business Combination, and CAC becoming a wholly owned subsidiary of Pubco as of the Closing of the Business Combination, each of the CAC Units, CAC Ordinary Shares and CAC Rights will receive the right to be converted into Pubco Ordinary Shares as described in the Business Combination Proposal and CAC securities will cease trading on Nasdaq (and following becoming a wholly owned subsidiary of Pubco CAC is expected to be deregistered under the Exchange Act and Pubco will become the reporting company under the Exchange Act).

Q:     What vote is required to approve the Proposals presented at the CAC EGM?

A:     The approval of each of the Business Combination Proposal, the Pubco Equity Plan Proposal, the ESPP Proposal, the Nasdaq Proposal, the Pubco Director Election Proposal, and the Adjournment Proposal is being proposed as an ordinary resolution, being the affirmative vote (in person or by proxy) of the holders of a majority of the CAC Ordinary Shares entitled to vote and actually casting votes thereon at the CAC EGM. The approval of each of the NTA Proposal and the Merger Proposal requires a special resolution under Cayman Islands law, being the affirmative vote (in person or by proxy) of the holders of at least two-thirds of the CAC Ordinary Shares entitled to vote and actually casting votes thereon at the CAC EGM. Accordingly, a shareholder’s failure to vote in person, online, or by proxy at the extraordinary general meeting will have no effect on the outcome of the vote on any of the Proposals.

Abstentions and broker non-votes, while considered present for the purposes of establishing a quorum, will not count as votes cast at the CAC EGM.

CAC’s Initial Shareholders, including the Sponsor and CAC’s directors and officers, currently hold an aggregate of 1,944,290 CAC Ordinary Shares, which is equal in aggregate to approximately 43.3% of the issued and outstanding CAC Ordinary Shares and have agreed in connection with the CAC IPO to vote all of their Founder Shares, all of their Private Placement shares and any other CAC equity securities that they hold in favor of the Business Combination Proposal. There are currently outstanding 4,494,439 CAC Ordinary Shares. As a result, assuming such presence and participation by CAC’s Initial Shareholders, including the Sponsor and CAC’s directors and officers, at the CAC EGM, no holders of the CAC Public Shares (other than any such persons) would be required to be present at the EGM in order to form a quorum, and 23.4% of the CAC Public Shares must vote in favor of the Business Combination Proposal in order for it to be approved.

Q:     May the Sponsor, CAC’s directors, officers, advisors, or any of their respective affiliates purchase Public Shares in connection with the Business Combination?

A:     In connection with the shareholder vote to approve the proposed Business Combination, the Sponsor, CAC’s directors, officers, advisors, or any of their respective affiliates may purchase Public Shares in privately negotiated transactions or in the open market either prior to or following the completion of the Business Combination, although they are under no obligation to do so. There is no limit on the number of Public Shares the Sponsor and CAC’s directors, officers, advisors, or any of their respective affiliates may purchase in such transactions, subject to compliance with applicable law and the rules of Nasdaq. However, any such purchases will be subject to limitations regarding possession of any material nonpublic information not disclosed to the seller of such shares and they will not make any such purchases if such purchases are prohibited by Regulation M or the tender offer rules under the Exchange Act or on any terms prohibited by the tender offer rules, to the extent applicable. Any such purchases may be effected at purchase prices that are no greater than the per share pro rata portion of the Trust Account. However, the Sponsor and CAC’s directors, officers, advisors, and their respective affiliates have no current commitments, plans, or intentions to engage in such transactions and have not formulated any terms or conditions for any such transactions. None of the funds in the Trust Account will be used to purchase Public Shares in such transactions. None of the Sponsor, or CAC’s directors, officers, advisors, or any of their respective affiliates will make any such purchases when they are in possession of any material non-public information not disclosed to the seller of such public shares or during a restricted period under Regulation M under the Exchange Act. Such a purchase could include a contractual acknowledgement that such shareholder, although still the record holder of such Public Shares, is no longer the beneficial owner thereof and therefore agrees not to exercise its redemption rights. In the event that the Sponsor or CAC’s directors, officers, advisors, or any of their

respective affiliates purchase Public Shares in privately negotiated transactions from Public Shareholders who have already elected to exercise their redemption rights, such selling shareholders would be required to revoke their prior elections to redeem their shares. The purpose of such share purchases and other transactions would be to decrease the number of redemptions to provide additional financing to the combined company following the closing of the Business Combination or to satisfy a closing condition in the Business Combination Agreement, where it appears that such requirement would otherwise not be met; however, pursuant to SEC guidance, if the Sponsor, CAC’s directors, officers, advisors, or any of their respective affiliates purchase Public Shares in privately negotiated transactions or in the open market prior to the completion of the Business Combination, such Public Shares would not be voted in favor of the Proposals. Any such purchases of CAC’s Public Shares may result in the completion of the Business Combination that may not otherwise have been possible. Any such purchases will be reported pursuant to Section 13 and Section 16 of the Exchange Act to the extent the purchasers are subject to such reporting requirements. Further, such purchases would be structured in compliance with the requirements of Rule 14e-5 under the Exchange Act, including, among others, that the SPAC will file a Current Report on Form 8-K with the SEC to disclose private arrangements entered into or significant private purchases made by any of the Sponsor or SPAC’s executive officers, directors and advisors, or their respective affiliates. In addition, if such purchases are made, the public “float” of CAC’s Ordinary Shares may be reduced and the number of beneficial holders of CAC’s securities may be reduced, which may make it difficult to maintain or obtain the quotation, listing or trading of CAC’s securities on a national securities exchange.

Q:     How many votes do I have at the CAC EGM?

A:     CAC shareholders are entitled to one vote at the CAC EGM for each CAC Ordinary Share held of record as of [    ], the record date for the CAC EGM. As of the close of business on the record date, there were [    ] outstanding CAC Ordinary Shares, which are held by CAC’s Public Shareholders, and [    ] outstanding CAC Ordinary Shares, which are held by CAC’s initial shareholders.

Q:     What constitutes a quorum at the CAC EGM?

A:     Holders of a majority in voting power of CAC Ordinary Shares issued and outstanding and entitled to vote at the CAC EGM, present in person, online, or by proxy, constitute a quorum. In the absence of a quorum, the chairman of the meeting has the power to adjourn the CAC EGM. As of the record date for the CAC EGM, an aggregate of [    ] CAC Ordinary Shares, in the aggregate, would be required to achieve a quorum. Abstentions will count as present for the purposes of establishing a quorum with respect to each Proposal.

Q:     How will the Sponsor and CAC’s directors and officers vote?

A:     The Sponsor and CAC’s directors and officers have agreed to vote any CAC Ordinary Shares owned by them in favor of the Business Combination and the other Proposals. Currently, they own approximately [•]% of the issued and outstanding CAC Ordinary Shares. See “The Business Combination Agreement and the Ancillary Documents — Ancillary Documents.”

Q:     What happens if the Business Combination Proposal is not approved?

A:     Under the CAC Articles, if the Business Combination Proposal is not approved and CAC does not otherwise consummate an alternative Initial Business Combination by January 22, 2027 (if CAC extends the period in full, in one month or more increments, as further described herein, or such later date as may be provided by amendment in accordance with the Existing CAC Charter) (the “Combination Period”), CAC will be required to dissolve and liquidate the Trust Account by returning the then remaining funds in such account to CAC’s Public Shareholders.

Q:     Do I have redemption rights?

A:     Pursuant to the CAC Articles, a Public Shareholder may request that CAC redeem all or a portion of its Public Shares for cash if the Business Combination is consummated. As a holder of Public Shares, you will be entitled to receive cash for any Public Shares to be redeemed only if you:

•        hold Public Shares or, if you hold Public Shares through CAC Units, you elect to separate your CAC Units into the underlying Public Shares and Rights prior to exercising your redemption rights with respect to the Public Shares;

•        submit a written request to Continental Stock Transfer & Trust Company, CAC’s transfer agent, in which you (1) request that CAC redeem all or a portion of your Public Shares for cash and (2) identify yourself as the beneficial holder of the Public Shares and provide your legal name, phone number, and address; and

•        deliver your Public Shares to Continental Stock Transfer & Trust Company, CAC’s transfer agent, physically or electronically using the DTC’s DWAC System.

Holders must complete the procedures for electing to redeem their Public Shares in the manner described above prior to 5:00 p.m., Eastern time, on [    ], 2026 (two business days before the extraordinary general meeting) in order for their shares to be redeemed.

Holders of CAC Units must elect to separate the CAC Units into the underlying CAC Ordinary Shares and CAC Rights prior to exercising redemption rights with respect to the Public Shares. If Public Shareholders hold their CAC Units in an account at a brokerage firm or bank, such Public Shareholders must notify their broker or bank that they elect to separate the CAC Units into the underlying Public Shares and Public Rights, or if a holder holds CAC Units registered in its own name, the holder must contact Continental Stock Transfer & Trust Company, CAC’s transfer agent, directly and instruct it to do so. The redemption rights include the requirement that a holder must identify itself to CAC in order to validly redeem its shares. Public Shareholders (other than the initial shareholders) may elect to exercise their redemption rights with respect to their Public Shares even if they vote “FOR” the Business Combination Proposal. If the Business Combination is not consummated, the Public Shares will be returned to the respective holder, broker, or bank. If the Business Combination is consummated, and if a Public Shareholder properly exercises its redemption right with respect to all or a portion of the Public Shares that it holds and timely delivers its shares to Continental Stock Transfer & Trust Company, CAC will redeem the related Public Shares for a per-share price, payable in cash, equal to the aggregate amount then on deposit in the Trust Account, including interest earned on the funds held in the Trust Account and not previously released to CAC, divided by the number of the then-outstanding CAC Public Shares, which redemption will completely extinguish Public Shareholders, rights as shareholders (including the right to receive further liquidation distributions, if any). For illustrative purposes, as of December 31, 2025, this would have amounted to approximately $10.37 per issued and outstanding Public Share. If a Public Shareholder exercises its redemption rights in full, then it will not own Public Shares or Pubco Ordinary Shares following the redemption. See “Extraordinary General Meeting of CAC Shareholders — Redemption Rights” for the procedures to be followed if you wish to exercise your redemption rights with respect to your Public Shares.

Q:     Will how I vote affect my ability to exercise redemption rights?

A:     No. You may exercise your redemption rights whether you vote your CAC Ordinary Shares for or against or abstain from voting on the Business Combination Proposal or any other Proposal described in this proxy statement/prospectus. As a result, the Business Combination can be approved by shareholders who will redeem their shares and no longer remain shareholders.

Q:     How do I exercise my redemption rights?

A:     In order to exercise your redemption rights, you must (1) if you hold your CAC Ordinary Shares through CAC Units, elect to separate your CAC Units into the underlying CAC Ordinary Shares and Rights prior to exercising your redemption rights with respect to the CAC Ordinary Shares and (2) prior to 5:00 p.m., Eastern time, on [    ], 2026 (two business days before the extraordinary general meeting), tender your shares physically or electronically and submit a request in writing that CAC redeem your CAC Ordinary Shares for cash to Continental Stock Transfer & Trust Company, CAC’s transfer agent, at the following address:

Continental Stock Transfer & Trust Company

One State Street 30th Floor, New York, NY 10004-1561

Attn: SPAC Redemption Team

Email: spacredemptions@continentalstock.com

Notwithstanding the foregoing, a Public Shareholder, together with any of his, her, or its affiliates or any other person with whom it is acting in concert or as a “group” (as defined in Section 13(d)(3) of the Exchange Act), will be restricted from seeking redemption rights with respect to his, her, or its shares or, if part of such a group, the group’s shares, in excess of 15% of the Public Shares included in the units sold in the CAC IPO. Accordingly, all Public Shares in excess of the 15% threshold beneficially owned by a Public Shareholder or group will not be redeemed for cash. In order to determine whether a shareholder is acting in concert or as a group with any other shareholder, CAC will require each Public Shareholder seeking to exercise redemption rights to certify to CAC whether such shareholder is acting in concert or as a group with any other shareholder. Shareholders seeking to exercise their redemption rights and opting to deliver physical certificates should allot sufficient time to obtain physical certificates from the transfer agent and time to effect delivery. It is CAC’s understanding that shareholders should generally allot at least two weeks to obtain physical certificates from the transfer agent. However, CAC does not have any control over this process and it may take longer than two weeks. Shareholders who hold their shares in street name will have to coordinate with their bank, broker, or other nominee to have the shares certificated or delivered electronically.

Holders of outstanding CAC Units must separate the underlying Public Shares and Public Rights prior to exercising redemption rights with respect to the Public Shares. If you hold CAC Units registered in your own name, you must deliver the certificate for such units or deliver such units electronically to DTC with written instructions to separate such units into CAC Public Shares and CAC Rights. This must be completed far enough in advance to permit the mailing of the Public Share certificates or electronic delivery of the Public Shares back to you so that you may then exercise your redemption rights with respect to the Public Shares following the separation of such Public Shares from the CAC Units.

If a broker, dealer, commercial bank, trust company, or other nominee holds your CAC Units, you must instruct such nominee to separate your CAC Units. Your nominee must send written instructions by facsimile to Continental Stock Transfer & Trust Company. Such written instructions must include the number of CAC Units to be split and the nominee holding such CAC Units. Your nominee must also initiate electronically, using DTC’s DWAC (deposit withdrawal at custodian) system, a withdrawal of the relevant CAC Units and a deposit of the corresponding number of Public Shares and Public Rights. This must be completed far enough in advance to permit your nominee to exercise your redemption rights with respect to the Public Shares following the separation of such Public Shares from the CAC Units. While this is typically done electronically on the same business day, you should allow at least one full business day to accomplish the separation. If you fail to cause your Public Shares to be separated in a timely manner, you will likely not be able to exercise your redemption rights.

Any demand for redemption, once made, may be withdrawn at any time until the deadline for exercising redemption requests (and submitting shares to the transfer agent) and thereafter, with CAC’s consent, until the consummation of to the Business Combination, or such other date and time as may be determined by the CAC Board in its sole discretion. If you delivered your Public Shares for redemption to the transfer agent and decide within the required timeframe not to exercise your redemption rights, you may request that the transfer agent return the shares (physically or electronically). You may make such request by contacting CAC’s transfer agent at the email address or address listed under the question “Who can help answer my questions?” below.

Q:     What are the U.S. federal income tax consequences of exercising my redemption rights?

A:     The receipt of cash by a beneficial holder of CAC Ordinary Shares in redemption of such stock will be a taxable event for U.S. federal income tax purposes in the case of a U.S. Holder (as defined below). See “Certain Tax Considerations — Certain Material U.S. Federal Income Tax Considerations” for additional information.

All Holders of CAC Ordinary Shares considering exercising their redemption rights are urged to consult with their tax advisors with respect to the potential tax consequences to them of the Business Combination and the exercise of their redemption rights.

Q:     What happens if a substantial number of Public Shareholders vote in favor of the Business Combination and exercise their redemption rights?

A:     Public Shareholders are not required to vote in respect of the Business Combination Proposal in order to exercise their redemption rights. Accordingly, the Business Combination may be consummated even though the funds available from the Trust Account and the number of Public Shareholders are reduced as a result of redemptions by Public Shareholders.

Q:     What are the possible sources and the extent of dilution that the Public Shareholders that elect not to redeem their shares will experience in connection with the Business Combination?

A:     After the completion of the Business Combination, Public Shareholders will own a significantly smaller percentage of Pubco than they currently own of CAC. Consequently, the Public Shareholders, as a group, will have reduced ownership and voting power in Pubco compared to their ownership and voting power in CAC. The table below assumes no debt or equity financing is consummated prior to, or in connection with, the closing of the Business Combination, including any sale of Pubco Shares or other equity securities of Pubco to Sponsor (or a Sponsor affiliate) that may be consummated in connection with the Business Combination in the event of an Overage Amount pursuant to the Business Combination Agreement, other than the $10.0 million in Transaction Financing already provided by SEALSQ on November 19, 2025. The following table illustrates the potential impact of redemptions on the ownership percentage of Public Shareholders in a range of redemption scenarios, with the maximum redemption scenario representing the redemption of all Public Shares.

____________

*        Due to rounding, percentages may not total 100%.

(1)      Reflects 2,550,149, CAC Ordinary Shares subject to redemption held by public shareholders as at January 16, 2026 and 857,143 Pubco Ordinary Shares which will be automatically issued upon the exchange of the Public Rights at Closing.

(2)      Reflects 26,000,000 Pubco Shares issued at the Closing of Business Combination to WISeSat shareholders in exchange for their respective holdings of Company Ordinary Shares and Company Class F Shares. Includes distribution by WISeKey of some of its Company Ordinary Shares in the Company to Maxim as compensation for advisory services as described in the table. The Company Class F Shares are exchanged for the Pubco Class F Shares as of the Closing, consisting of 11,956,922 Pubco Class F Shares exchanged and issued to WISeKey and 1,040,478 Pubco Class F Shares exchanged and issued to SEALSQ. The Pubco Class F Shares are held at Closing by WISeKey and SEALSQ and are not transferable. The Pubco Class F Shares confer a number of votes per Class F Share, on any matter that is submitted to a vote of Pubco shareholders that would cause the total votes of all Pubco Class F Shares to equal 49.99% of the voting power of all Pubco Shares. For more information see “Description of Pubco’s Securities.”

(3)     Although the table reflects that WISeKey would hold voting power of 50%, because the Class F Shareholders Agreement provides that the majority holder of outstanding Pubco Class F Shares can vote on behalf of all of the holders of Pubco Class F Shares, effectively 49.99% of the voting power is held by WISeKey. The 50% amount is a rounded amount from such 49.99% of the voting power held by WISeKey. For more information about such Pubco Class F Shares, see “Description of Pubco’s

Securities.” As described in such section, only the majority holder of Pubco Class F Shares, which is WISeKey, can exercise such voting rights. Accordingly, although SEALSQ Corp. has 49.9% voting rights from such shares, it can only exercise such rights if it is majority owner of Pubco Class F Shares in lieu of WISeKey, and otherwise would only have voting rights attributable to its holdings of Pubco Ordinary Shares.

(4)      Assumes that CAC public shareholders holding 50% of the approximately 2,550,149 CAC Ordinary Shares subject to possible redemption will exercise their redemption rights upon consummation of the Business Combination at a redemption price as of January 16, 2026, the date of CAC’s last extraordinary general meeting, would have been approximately $10.387 per share.

(5)      Assumes that all of CAC public shareholders holding approximately 2,550,149 CAC Ordinary Shares subject to possible redemption will exercise their redemption rights upon consummation of the Business Combination at a redemption price as of January 16, 2026, the date of CAC’s last extraordinary general meeting, would have been approximately $10.387 per share.

(6)      Assumes that Pubco Class F Shares are not converted into Pubco Ordinary Shares. Pubco Class F Shares are convertible at the option of the holder on a one for one basis into Pubco Ordinary Shares. For more information about such Pubco Class F Shares, see “Description of Pubco’s Securities.” If Pubco Class F Shares were fully converted then the number of Pubco Ordinary Shares would be the number reflected on the foregoing row in the table, being “Total Shares” beginning with 31,385,052.

Dilution

In accordance with Item 1604(c) of Regulation S-K, the dilution information provided below gives effect to material probable or consummated transactions affecting CAC’s net tangible book value, while excluding the de-SPAC transaction itself. Net tangible book value as of December 31, 2025 is calculated as total tangible assets minus total liabilities and mezzanine equity.

The table below gives effect to the funds expected to be released from the Trust Account under each redemption scenario, after giving effect to the January 16, 2026 redemption event described below, as well as estimated CAC transaction costs of $1,136,000 and the $119,475 estimated fair value of Mr. Johnson’s Director Option Shares, as disclosed elsewhere in this proxy statement/prospectus. Although the exercise window for the Director Option Shares opens only after the Closing, the adjustment has been included because the option was granted to a CAC director in connection with his appointment and is directly linked to CAC’s activities.

On January 16, 2026, CAC held an extraordinary general meeting of shareholders in connection with the extension of the period available to consummate an initial business combination. Just prior to such redemptions, CAC had 6,000,000 Public Shares outstanding and a Trust Account balance of 62,319,389. In connection with that meeting, holders of 3,449,851 CAC Ordinary Shares exercised redemption rights reducing the Trust Account by (35,832,101). Following such redemptions, 2,550,149 CAC Public Shares remained outstanding, and the Trust Account balance was $26,487,288, representing approximately $10.387 per remaining Public Share.

Accordingly, the net tangible book value as of December 31, 2025 has been adjusted to reflect the funds released from the Trust Account in connection with the January 16, 2026 redemptions and the additional funds assumed to be released from the Trust Account under each redemption scenario presented below: no further redemptions, 50% redemptions and 100% redemptions of the remaining CAC Public Shares.

If the NTA Requirement Amendment Proposal (Proposal No. 1) is not approved by CAC shareholders, the Business Combination may be consummated only if CAC has net tangible assets of at least $5,000,001 upon closing of the Business Combination. Based on the 2,550,149 CAC Public Shares outstanding after the January 16, 2026 redemptions and the corresponding Trust Account balance of $26,487,288, the maximum number of remaining CAC Public Shares that may be redeemed while satisfying the NTA Requirement would be 1,965,140, or approximately 77% of the remaining CAC Public Shares. Any redemptions above that level would cause CAC’s net tangible book value to fall below $5,000,001, absent approval of the NTA Requirement Amendment Proposal or other offsetting adjustments.

____________

(1)      50% Redemption Scenario: Assumes 50% of all 2,550,149 CAC publicly traded shares have shareholders who elect to redeem those shares and that the conditions to Closing are satisfied.

(2)      Maximum Redemption Scenario: Assumes all 2,550,149 CAC publicly traded shares have shareholders who elect to redeem those shares and that the conditions to Closing are satisfied.

(3)      Reflects Exchange Shares estimates as of the date of this proxy statement/prospectus that include 18,387,652 Pubco Ordinary Shares and 12,497,700 Pubco Class F Shares. The exact amount of Exchange Shares will be allocated between Pubco Ordinary Shares and Pubco Class F Shares in proportion to the number of Company Ordinary Shares and Company Class F Shares owned by shareholders of the Seller at the time of the Share Exchange.

In accordance with Item 1604(c)(1) of Regulation S-K, the table below presents, at each redemption level, the valuation at or above which the potential dilution results in the amount of non-redeeming shareholders’ interest per share being at least the IPO price per share of ordinary shares.

Sources of dilution that may or not be automatically convertible upon the consummation of the Business Combination are presented above.

Q:     Do I have appraisal rights if I object to the proposed Business Combination?

A:     Holders of record of CAC Ordinary Shares may have appraisal rights in connection with the Business Combination under the Cayman Companies Act. Holders of record of CAC Ordinary Shares wishing to exercise such statutory dissenter rights and make a demand for payment of the fair value for his, her or its CAC Ordinary Shares must give written objection to the Merger to CAC prior to the shareholder vote to approve the Merger and follow the procedures set out in Section 238 of the Cayman Companies Act. These statutory appraisal rights are separate to and mutually exclusive of the right of CAC’s Public Shareholders to demand that their Public Shares are redeemed for cash for a pro rata share of the funds on deposit in the Trust Account in accordance with the CAC Articles. It is possible that if a CAC shareholder exercises appraisal rights, the fair value of the CAC Ordinary Shares determined under Section 238 of the Cayman Companies Act could be more than, the same as, or less than such holder would obtain if he, she, or it exercised his, her or its redemption rights as described herein. CAC believes that such fair value would equal the amount that CAC shareholders would obtain if they exercise their redemption rights as described herein. CAC shareholders need not vote against any of the Proposals at the extraordinary general meeting in order to exercise appraisal rights under the Cayman Companies Act. A CAC shareholder which elects to exercise appraisal rights must do so in respect of all of the CAC Ordinary Shares that person holds and will lose their right to exercise their redemption rights as described herein. See “Appraisal Rights under the Cayman Islands Law.”

Q:     What happens to the funds deposited in the Trust Account after consummation of the Business Combination?

A:     CAC intends to use a portion of the funds held in the Trust Account to pay holders of the CAC Public Shares who exercise redemption rights and to pay fees and expenses associated with the Business Combination (including certain deferred underwriting discounts and commissions payable to underwriters for the CAC IPO). The remaining balance in the Trust Account will be used for general corporate purposes of Pubco.

Q:     What happens if the Business Combination is not consummated or is terminated?

A:     There are certain circumstances under which the Business Combination Agreement may be terminated. See the subsection entitled “The Business Combination Agreement and the Ancillary Documents — The Business Combination Agreement — Termination of the Business Combination Agreement” for additional information regarding the parties’ specific termination rights. In accordance with the CAC Articles, if an Initial Business Combination is not consummated by January 22, 2027 (if CAC extends the period in full, as further described herein, or such later date as may be provided by amendment in accordance with the CAC Articles), CAC will (1) cease all operations except for the purpose of winding up, (2) as promptly as reasonably possible but not more than 10 business days thereafter, redeem the Public Shares, at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the Trust Account, including interest earned on the funds held in the Trust Account and not previously released to CAC, divided by the number of the then-outstanding CAC Public Shares, which redemption will completely extinguish Public Shareholders, rights as shareholders (including the right to receive further liquidation distributions, if any), and (3) as promptly as reasonably possible following such redemption, subject to the approval of CAC’s remaining shareholders and the CAC Board, liquidate and dissolve, subject in each case of (2) and (3) above to CAC’s obligations under Cayman Islands law to provide for claims of creditors and in all cases subject to the other requirements of applicable law.

It is expected that the amount of any distribution CAC’s Public Shareholders will be entitled to receive upon its dissolution will be approximately the same as the amount they would have received if they had redeemed their shares in connection with the Business Combination, subject in each case to CAC’s obligations under Cayman Islands law to provide for claims of creditors and other requirements of applicable law. Holders of the CAC Founder Shares have waived any right to any liquidating distributions with respect to those shares.

In the event of liquidation, there will be no distribution with respect to the outstanding CAC Rights. Accordingly, the CAC Rights will expire worthless.

Q:     When is the Business Combination expected to be consummated?

A:     It is currently anticipated that the Business Combination will be consummated promptly following the CAC EGM to be held on [    ], 2026, provided that all the requisite shareholder approvals are obtained and other conditions to the consummation of the Business Combination have been satisfied or waived. For a description of the conditions for the completion of the Business Combination, see the subsection entitled “The Business Combination Agreement and the Ancillary Documents — The Business Combination Agreement.”