W. R. Berkley (SBXD holder) discloses 1.92M-share, 9.4% position in SilverBox

Rhea-AI Filing Summary

W. R. Berkley Corporation, through subsidiary Berkley Insurance Company, reports beneficial ownership of Class A Ordinary Shares of SilverBox Corp IV. 1,923,442 shares are beneficially owned, representing 9.4% of the class. The filing states shared voting power and shared dispositive power over all 1,923,442 shares, with no sole voting or dispositive power reported.

Key Figures

Beneficially owned shares: 1,923,442 shares Percent of class: 9.4% Shared voting power: 1,923,442 shares +2 more

5 metrics

Beneficially owned shares 1,923,442 shares Class A Ordinary Shares of SilverBox Corp IV reported by W. R. Berkley Corporation

Percent of class 9.4% Ownership percentage of SilverBox Corp IV Class A Ordinary Shares

Shared voting power 1,923,442 shares Shares over which W. R. Berkley Corporation has shared voting power

Shared dispositive power 1,923,442 shares Shares over which W. R. Berkley Corporation has shared dispositive power

Par value per share $0.0001 per share Par value of SilverBox Corp IV Class A Ordinary Shares

Key Terms

beneficially owned, shared voting power, shared dispositive power, Schedule 13G, +1 more

5 terms

beneficially owned financial

"Item 4. | Ownership (a) | Amount beneficially owned: 1,923,442"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

shared voting power financial

"(ii) Shared power to vote or to direct the vote: 1,923,442"

Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.

shared dispositive power financial

"(iv) Shared power to dispose or to direct the disposition of: 1,923,442"

Schedule 13G regulatory

"Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

CUSIP financial

"(e) | CUSIP No.: G81354105"

A CUSIP is a nine-character alphanumeric code that uniquely identifies a U.S. or Canadian financial security—such as a stock, bond, or fund share—like a Social Security number for an investment. It matters to investors because brokers, exchanges and record-keepers use the CUSIP to match trades, track ownership, settle transactions and pull accurate records, reducing errors and ensuring money and securities go to the right place.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 08/06/2026 - 05:08 PM Accepted by SEC EDGAR 08/06/2026 - 05:07 PM Learn about SEC filing dates

FAQ

What percentage of SilverBox Corp IV (SBXD) does W. R. Berkley Corporation report owning?

W. R. Berkley Corporation reports beneficial ownership of 9.4% of SilverBox Corp IV’s Class A Ordinary Shares. This stake reflects 1,923,442 shares held with shared voting and dispositive power.

How many SilverBox Corp IV (SBXD) shares does W. R. Berkley Corporation beneficially own?

W. R. Berkley Corporation reports beneficial ownership of 1,923,442 Class A Ordinary Shares of SilverBox Corp IV. All these shares are held with shared voting and shared dispositive power, and no sole power is reported.

Which entities are listed as holders of SBXD shares in this Schedule 13G/A?

The filing lists W. R. Berkley Corporation and its subsidiary Berkley Insurance Company as beneficial owners of 1,923,442 SilverBox Corp IV shares, each reporting identical 9.4% ownership with shared voting and dispositive power.

Does W. R. Berkley Corporation have sole voting power over its SBXD shares?

No. The Schedule 13G/A reports 0 shares with sole voting power and 1,923,442 shares with shared voting power. Sole dispositive power is also 0, with all shares under shared dispositive power.

What class of SilverBox Corp IV (SBXD) securities is covered by this Schedule 13G/A?

The filing covers Class A Ordinary Shares of SilverBox Corp IV, each with a par value of $0.0001 per share. The associated CUSIP for this class is G81354105.

Where are W. R. Berkley Corporation and SilverBox Corp IV based according to this filing?

W. R. Berkley Corporation’s principal office is at 475 Steamboat Road, Greenwich, CT 06830. SilverBox Corp IV’s principal executive offices are at 8701 Bee Cave Road, East Building, Suite 310, Austin, Texas 78746.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 2)

SILVERBOX CORP IV

(Name of Issuer)

Class A Ordinary Shares, par value $0.0001 per share

(Title of Class of Securities)

G81354105

(CUSIP Number)

06/30/2026

(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)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): G81354105

1

Names of Reporting Persons

W. R. Berkley Corporation

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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,923,442.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,923,442.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,923,442.00

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)

9.4 %

12

Type of Reporting Person (See Instructions)

CO

SCHEDULE 13G

CUSIP Number(s): G81354105

1

Names of Reporting Persons

Berkley Insurance Company

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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,923,442.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,923,442.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,923,442.00

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)

9.4 %

12

Type of Reporting Person (See Instructions)

CO, IC

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, Texas, 78746
Item 2.
(a)	Name of person filing: W. R. Berkley Corporation
(b)	Address or principal business office or, if none, residence: 475 Steamboat Road Greenwich, CT 06830
(c)	Citizenship: US
(d)	Title of class of securities: Class A Ordinary Shares, par value $0.0001 per share
(e)	CUSIP No.: G81354105
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).
Item 4.	Ownership
(a)	Amount beneficially owned: 1,923,442
(b)	Percent of class: 9.4 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 0
	(ii) Shared power to vote or to direct the vote: 1,923,442
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 1,923,442
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
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.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. See Exhibit 99.1
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.

W. R. Berkley Corporation

Signature:	/s/ Richard M. Baio
Name/Title:	Richard M. Baio/Executive Vice President and Chief Financial Officer
Date:	08/05/2026

Berkley Insurance Company

Signature:	/s/ Richard M. Baio
Name/Title:	Richard M. Baio/Executive Vice President and Treasurer
Date:	08/05/2026