Quantumsphere: Berkley reports 9.5% passive stake

Quantumsphere Acquisition Corp (QUMS) is the issuer of Class A ordinary shares for which W. R. Berkley Corporation and Berkley Insurance Company each reported beneficial ownership of 1,081,561 shares, or 9.5% of the class.

Available on EDGAR 11/09/2026 - 06:38 PM EST Accepted by SEC EDGAR 11/09/2026 - 06:37 PM EST Learn about SEC filing dates

Rhea-AI Filing Summary

Quantumsphere Acquisition Corp (QUMS) is the issuer of Class A ordinary shares for which W. R. Berkley Corporation and Berkley Insurance Company each reported beneficial ownership of 1,081,561 shares, or 9.5% of the class. Each reported shared voting and shared dispositive power over 1,081,561 shares, with zero sole voting and sole dispositive power. The stated event date is September 30, 2026.

Key Figures

Beneficial ownership: 1,081,561 shares Class ownership: 9.5% Shared voting power: 1,081,561 shares +1 more

4 metrics

Beneficial ownership 1,081,561 shares Reported by each of W. R. Berkley Corporation and Berkley Insurance Company

Class ownership 9.5% Reported by each reporting person

Shared voting power 1,081,561 shares Reported by each reporting person

Shared dispositive power 1,081,561 shares Reported by each reporting person

Key Terms

beneficially owned, Shared Voting Power, Shared Dispositive Power

3 terms

beneficially owned regulatory

"Aggregate Amount Beneficially Owned by Each Reporting Person"

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 regulatory

"Shared Voting Power 1,081,561.00"

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 regulatory

"Shared Dispositive Power 1,081,561.00"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many QUMS shares did W. R. Berkley report beneficially owning?

W. R. Berkley Corporation and Berkley Insurance Company each reported beneficial ownership of 1,081,561 QUMS Class A ordinary shares, representing 9.5% of the class.

What voting and disposition powers were reported for QUMS shares?

Each reporting person reported shared voting power and shared dispositive power over 1,081,561 shares, with zero sole voting and sole dispositive power.

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

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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

Quantumsphere Acquisition Corp

(Name of Issuer)

Class A ordinary shares, par value $0.0001 per share

(Title of Class of Securities)

(CUSIP Number)

09/30/2026

(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 No.

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 1,081,561.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,081,561.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,081,561.00

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)

9.5 %

12

Type of Reporting Person (See Instructions)

CO

SCHEDULE 13G

CUSIP No.

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 1,081,561.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,081,561.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,081,561.00

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)

9.5 %

12

Type of Reporting Person (See Instructions)

CO, IC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Quantumsphere Acquisition Corp
(b)	Address of issuer's principal executive offices: 1185 Avenue of the Americas, Suite 304, New York, New York, 10036
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.:
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: 1,081,561
(b)	Percent of class: 9.5 %
(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: 1,081,561
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 1,081,561
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:	11/09/2026

Berkley Insurance Company

Signature:	/s/ Richard M. Baio
Name/Title:	Richard M. Baio/Executive Vice President and Treasurer
Date:	11/09/2026