W.R. Berkley (MCGA) discloses 1,645,570-share, 9.2% holding

Rhea-AI Filing Summary

W. R. Berkley Corporation reports 9.2% beneficial ownership of Yorkville Acquisition Corp. Class A ordinary shares. The filing shows 1,645,570 shares beneficially owned with shared voting and dispositive power as of 03/31/2026. The filing is a Schedule 13G disclosure by a parent/control entity and is signed by Richard M. Baio.

Insights

Corporate Governance Analyst

13G shows a passive substantial stake with shared control.

The filing lists 1,645,570 shares representing 9.2% ownership of Class A ordinary shares as of 03/31/2026. Voting and dispositive power are reported as shared rather than sole, consistent with a parent/subsidiary holding structure.

Future disclosures may reflect changes in ownership; timing not specified in the provided excerpt.

Equity Markets Specialist

Stake size is notable but falls below typical control thresholds.

An ownership stake of 1,645,570 shares (9.2%) is material for disclosure but below majority control; the role is passive as presented. The filing identifies shared voting/dispositive powers, suggesting coordinated ownership via affiliates.

Market impact depends on whether these shares are actively traded by the holders; the excerpt provides no trading intent.

Key Figures

Shares beneficially owned: 1,645,570 shares Percent of class: 9.2% CUSIP: G98659116 +2 more

5 metrics

Shares beneficially owned 1,645,570 shares Beneficial ownership of Class A ordinary shares

Percent of class 9.2% Percent of Class A ordinary shares owned as of 03/31/2026

CUSIP G98659116 Identifier for Class A ordinary shares

Filing type Schedule 13G Beneficial ownership disclosure

Signature date 05/07/2026 Signed by Richard M. Baio

Key Terms

Schedule 13G, Beneficially owned, Shared dispositive power

3 terms

Schedule 13G regulatory

"Item 1. (a) Name of issuer: YORKVILLE ACQUISITION CORP."

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.

Beneficially owned financial

"Item 4. (a) Amount beneficially owned: 1,645,570"

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 dispositive power financial

"Item 4. (iv) Shared power to dispose: 1,645,570"

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

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Accepted by SEC EDGAR 05/08/2026 - 09:09 AM Learn about SEC filing dates

FAQ

What does W. R. Berkley Corporation report in this Schedule 13G for MCGA?

The filing reports 1,645,570 shares beneficially owned, equal to 9.2% of Class A ordinary shares as of 03/31/2026. It lists shared voting and dispositive power and is signed by Richard M. Baio on 05/07/2026.

Does the Schedule 13G indicate W. R. Berkley has sole voting control of MCGA shares?

No. The filing states 0 shares with sole voting power and 1,645,570 shares with shared voting power, indicating shared rather than sole voting control over the reported position.

Who signed the Schedule 13G for W. R. Berkley Corporation (MCGA)?

The Schedule 13G is signed by Richard M. Baio in his capacity as Executive Vice President and Chief Financial Officer and as Executive Vice President and Treasurer, dated 05/07/2026.

What CUSIP and class are associated with this filing for MCGA?

The filing covers Class A ordinary shares, par value $0.0001 per share, with CUSIP G98659116. The ownership disclosure pertains specifically to that class of securities.

Is the 9.2% stake held directly or through subsidiaries according to the filing?

The filing indicates the position is reported by W. R. Berkley Corporation with shared powers and references a subsidiary acquisition exhibit; it reflects a parent/subsidiary reporting structure rather than a simple direct holding.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

YORKVILLE ACQUISITION CORP.

(Name of Issuer)

Class A ordinary shares, par value $0.0001 per share

(Title of Class of Securities)

G98659116

(CUSIP Number)

03/31/2026

(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): G98659116

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 1,645,570.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,645,570.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,645,570.00

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)

9.2 %

12

Type of Reporting Person (See Instructions)

CO

SCHEDULE 13G

CUSIP Number(s): G98659116

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 1,645,570.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,645,570.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,645,570.00

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)

9.2 %

12

Type of Reporting Person (See Instructions)

CO, IC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: YORKVILLE ACQUISITION CORP.
(b)	Address of issuer's principal executive offices: 1012 Springfield Avenue, Mountainside, New Jersey, 07092
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 Number(s): G98659116
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: 1,645,570
(b)	Percent of class: 9.2 %
(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: 1,645,570
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 1,645,570
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:	05/07/2026

Berkley Insurance Company

Signature:	/s/ Richard M. Baio
Name/Title:	Richard M. Baio/Executive Vice President and Treasurer
Date:	05/07/2026