Polar Asset Mgmt Files Amendment: 7.2% Stake in SBXD

Rhea-AI Filing Summary

Polar Asset Management Partners Inc. reports beneficial ownership of 1,480,000 Class A ordinary shares of Silverbox Corp IV, representing 7.2% of the class. The filing is a Schedule 13G/A amendment and shows Polar holds sole voting and sole dispositive power over the shares.

The filing states Polar serves as investment adviser to Polar Multi-Strategy Master Fund and that the securities are held in the ordinary course of business and not for the purpose of changing or influencing control of the issuer. The disclosure provides clarity on a material passive stake above 5% in Silverbox Corp IV.

Positive

• Reporting of a material ownership stake: 1,480,000 shares equals 7.2% of the Class A shares, exceeding the 5% disclosure threshold.
• Clear disclosure of sole voting and sole dispositive power and certification that the shares are held in the ordinary course of business and not to influence control.

Negative

• None.

Insights

Financial Analyst

TL;DR: A 7.2% passive stake by Polar signals a material, non-activist ownership position with sole voting and dispositive power.

Polar Asset Management Partners Inc. reports beneficial ownership of 1,480,000 Class A shares, equal to 7.2% of the class, and discloses sole voting and sole dispositive authority. The statement certifies the holdings are in the ordinary course of business and not intended to influence control, consistent with a Schedule 13G approach rather than an activist 13D filing. For investors, this clarifies ownership concentration without signaling an immediate governance challenge.

Corporate Governance Expert

TL;DR: The filing documents a significant but passive ownership that should be monitored for potential future activity despite current non-control intent.

From a governance perspective, Polar’s disclosure of sole voting and sole dispositive power over 1,480,000 shares (7.2%) is material because it establishes a clear single-party influence path even though the certifying language states no intent to seek control. The Schedule 13G/A format and the certification language indicate a passive posture today; future amendments or switches to a Schedule 13D would materially change the governance outlook.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

Silverbox Corp IV

(Name of Issuer)

Class A ordinary shares, par value $0.0001 per share

(Title of Class of Securities)

G81354113

(CUSIP Number)

06/30/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. G81354113

1

Names of Reporting Persons

Polar Asset Management Partners Inc.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

ONTARIO, CANADA

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 1,480,000.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 1,480,000.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,480,000.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

7.2 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Silverbox Corp IV
(b)	Address of issuer's principal executive offices: 8701 Bee Cave Road East Building, Suite 310, Austin, TX, 78746
Item 2.
(a)	Name of person filing: This statement is filed by Polar Asset Management Partners Inc., a company incorporated under the laws of Ontario, Canada, which serves as the investment advisor to Polar Multi-Strategy Master Fund, a Cayman Islands exempted company ("PMSMF") with respect to the shares directly held by PMSMF.
(b)	Address or principal business office or, if none, residence: 16 York Street, Suite 2900, Toronto, Ontario, M5J 0E6
(c)	Citizenship: Canada
(d)	Title of class of securities: Class A ordinary shares, par value $0.0001 per share
(e)	CUSIP No.: G81354113
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
	The Reporting Person is an investment fund manager, portfolio manager, exempt market dealer and commodity trading manager registered with the Ontario Securities Commission.
Item 4.	Ownership
(a)	Amount beneficially owned: 1480000
(b)	Percent of class: 7.2 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 1480000
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 1480000
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Polar Asset Management Partners Inc.

Signature:	Andrew Ma
Name/Title:	Chief Compliance Officer
Date:	08/14/2025

FAQ

How many Silverbox Corp IV (SBXD) shares does Polar Asset Management own?

Polar Asset Management Partners Inc. beneficially owns 1,480,000 Class A shares of Silverbox Corp IV.

What percentage of SBXD does Polar's holding represent?

The reported position represents 7.2% of the Class A ordinary shares outstanding.

Does Polar have voting or dispositive power over the shares?

Yes. The filing reports Polar has sole voting power and sole dispositive power over the 1,480,000 shares.

Is this filing an amendment or an initial Schedule 13G?

This statement is filed as a Schedule 13G/A amendment.

Is Polar seeking to change control of Silverbox Corp IV according to the filing?

The filing includes a certification that the securities are held in the ordinary course of business and were not acquired to change or influence control of the issuer.

Who is the reported filing entity and what role does it serve?

The reporting person is Polar Asset Management Partners Inc., which serves as investment adviser to Polar Multi-Strategy Master Fund with respect to the reported shares.