As of November 10, 2026, 3 holders' latest Schedule 13D or 13G filings report owning 5% or more of Quantumsphere Acquisition Corp. The largest reported stake is Whiteowl Holdings LLC's, at 27.41%. 8 filings are on record since September 15, 2025 (Schedule 13D, September 15, 2025).
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Key facts
- · Reporting person: W. R. Berkley Corporation · Sole voting: 0 · Shared voting: 1,081,561 · Sole dispositive: 0 · Shared dispositive: 1,081,561 · SCHEDULE 13G/A, 2026-11-09
- · Reporting person: Wolverine Asset Management, LLC · Sole voting: 0 · Shared voting: 335,957 · Sole dispositive: 0 · Shared dispositive: 335,957 · SCHEDULE 13G/A, 2026-10-06
- · Holder: W. R. Berkley Corporation · Percent: 7.7% · SCHEDULE 13G
- · Holder: Highbridge Capital Management, LLC · Percent: 0% · SCHEDULE 13G/A
- · Holder: Mizuho Financial Group, Inc. · Percent: 6.3% · SCHEDULE 13G
Quantumsphere Acquisition Corp has 8 Schedule 13D or 13G filings on record since 2025-09-15. 3 holders' latest filing reports 5% or more of class a ordinary shares, par value $0.0001 per share. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| Whiteowl Holdings LLC | 27.41% | 3,126,650 | SCHEDULE 13D, 2025-09-15 | 2025-08-05 |
| W. R. Berkley Corporation | 9.5% | 1,081,561 | SCHEDULE 13G/A, 2026-11-09 | 2026-09-30 |
| Mizuho Financial Group, Inc. | 6.3% | 718,086 | SCHEDULE 13G, 2026-02-12 | 2025-12-31 |
| Wolverine Asset Management, LLC | 2.95% | 335,957 | SCHEDULE 13G/A, 2026-10-06 | 2026-09-30 |
| Highbridge Capital Management, LLC | 0% | 0 | SCHEDULE 13G/A, 2026-02-17 | 2025-12-31 |
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Keep reading
More on Quantumsphere Acquisition Corp and the records around it.
Companies that share a holder
- Mizuho Financial Group, Inc. also filed stake reports on 74 other companies: Aeon Acquisition I Corp. (Aug 2026), Alpex Acquisition Corp (Aug 2026), Aperture AC (Aug 2026)
- WOLVERINE ASSET MANAGEMENT LLC also filed stake reports on 75 other companies: Black Hawk Acquisition Corp (Nov 2026), AmperCap Acquisition Company (Oct 2026), BTC Development Corp. (Oct 2026)
- HIGHBRIDGE CAPITAL MANAGEMENT LLC also filed stake reports on 83 other companies: Aeon Acquisition I Corp. (Aug 2026), Alpex Acquisition Corp (Aug 2026), Aperture AC (Aug 2026)
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What the Full Report on Quantumsphere Acquisition Corp covers
The Short Answer
Which Company This Is
What They Do, And How The Money Works
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Voting and dispositive power, as filed
| Reporting person | Sole voting | Shared voting | Sole dispositive | Shared dispositive | Filing |
|---|---|---|---|---|---|
| W. R. Berkley Corporation | 0 | 1,081,561 | 0 | 1,081,561 | SCHEDULE 13G/A, 2026-11-09 |
| Berkley Insurance Company | 0 | 1,081,561 | 0 | 1,081,561 | SCHEDULE 13G/A, 2026-11-09 |
| Wolverine Asset Management, LLC | 0 | 335,957 | 0 | 335,957 | SCHEDULE 13G/A, 2026-10-06 |
| Wolverine Holdings, LLC | 0 | 335,957 | 0 | 335,957 | SCHEDULE 13G/A, 2026-10-06 |
| Christopher L. Gust | 0 | 335,957 | 0 | 335,957 | SCHEDULE 13G/A, 2026-10-06 |
| Robert R. Bellick | 0 | 335,957 | 0 | 335,957 | SCHEDULE 13G/A, 2026-10-06 |
The latest filing identifies Quantumsphere Acquisition Corp by CUSIP G7387B106 and gives its principal executive office as 1185 Avenue of the Americas, Suite 304, New York, NY 10036 (SCHEDULE 13G/A, 2026-11-09).
What the percentages are based on
WAM may be deemed the beneficial owner of 2.95% of the Issuer's outstanding Ordinary Shares and each of Wolverine Holdings, Mr. Bellick, and Mr. Gust may be deemed the beneficial owner of 2.95% of the Issuer's outstanding Ordinary Shares.Wolverine Asset Management, LLC, SCHEDULE 13G/A, 2026-10-06
Purpose of Transaction (Item 4)
Whiteowl Holdings LLC
In connection with the organization of the Issuer, on August 29, 2024, pursuant to a Subscription Agreement, the Issuer issued an aggregate of 2,875,000 ordinary shares as Founder Shares, to the Sponsor for an aggregate purchase price of $25,000. On May 6, 2025, our Sponsor surrendered 460,000 founder shares for no consideration to us for cancellation and as a result, our Sponsor held 2,415,000 founder shares as of May 6, 2025. On August 5, 2025, the Issuer and the Sponsor entered into the First Amendment to the Subscription Agreement, pursuant to which the purchased amount of shares was adjusted to 2,898,000 ordinary shares, of which 378,000 are subject to forfeiture if the underwriters' over-allotment option is not exercised in full. Simultaneously with the consummation of the Issuer's initial public offering, the Sponsor purchased 228,650 units ("Placement Units") of the Issuer at $10.00 per Placement Unit, as more fully described in Item 6 of this Schedule 13D, which information is incorporated herein by reference. Each Placement Unit consists of one ordinary share and one right to receive one-seventh (1/7) of one ordinary share upon the consummation of the Issuer's initial business combination (as described more fully in the Issuer's Final Prospectus dated August 7, 2025). On July 25, 2025, the Sponsor and its member entered into the First Amendment to the Operating Agreement, whereby 83.13% of the Sponsor's interest was transferred to Wealthwise Solutions LTD, making …The first part of Item 4 of the SCHEDULE 13D filed 2025-09-15; the filing has the rest
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-09-15 | Whiteowl Holdings LLC | 27.41% | SCHEDULE 13D |
| 2025-11-07 | Wolverine Asset Management LLC | 5.03% | SCHEDULE 13G |
| 2025-11-14 | Highbridge Capital Management LLC | 5.3% | SCHEDULE 13G |
| 2026-02-12 | Mizuho Financial Group, Inc. | 6.3% | SCHEDULE 13G |
| 2026-02-17 | Highbridge Capital Management, LLC | 0% | SCHEDULE 13G/A |
| 2026-08-06 | W. R. Berkley Corporation | 7.7% | SCHEDULE 13G |
| 2026-10-06 | Wolverine Asset Management, LLC | 2.95% | SCHEDULE 13G/A |
| 2026-11-09 | W. R. Berkley Corporation | 9.5% | SCHEDULE 13G/A |
Questions about who owns Quantumsphere Acquisition Corp
Who owns Quantumsphere Acquisition Corp?
On this page, 3 holders' latest ownership filings report 5% or more of Quantumsphere Acquisition Corp: Whiteowl Holdings LLC (27.41%, Schedule 13D, filed 2025-09-15), W. R. Berkley Corporation (9.5%, Schedule 13G/A, filed 2026-11-09) and Mizuho Financial Group, Inc. (6.3%, Schedule 13G, filed 2026-02-12).
Who are the largest shareholders of Quantumsphere Acquisition Corp?
By the share each holder's latest filing reports, the largest holders of Quantumsphere Acquisition Corp on this page are Whiteowl Holdings LLC (27.41%), W. R. Berkley Corporation (9.5%) and Mizuho Financial Group, Inc. (6.3%).
When did Whiteowl Holdings LLC buy into Quantumsphere Acquisition Corp?
The filings give report dates, not purchase dates. The earliest filing from Whiteowl Holdings LLC on this page is the Schedule 13D, filed 2025-09-15, reporting 27.41%.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 8 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
Also on the record for Quantumsphere Acquisition Corp
| Date | Record | Figure | Our page | Source |
|---|---|---|---|---|
| August 7, 2025 | IPO filing, Form 424B4 | $10 a share | IPO filings | Source |
| July 30, 2025 | IPO filing, Form S-1/A | — | IPO filings | Source |
| July 24, 2025 | IPO filing, Form S-1/A | — | IPO filings | Source |
| July 10, 2025 | IPO filing, Form S-1/A | — | IPO filings | Source |
| May 30, 2025 | IPO filing, Form S-1 | — | IPO filings | Source |
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Where this comes from
Anyone who comes to own more than 5% of a class of a listed company's voting shares has to tell the SEC. A holder who may seek to change or influence the company files Schedule 13D, and has to say in Item 4, "Purpose of Transaction", what it intends to do. A holder with no such intent, such as many index and passive funds, may file the shorter Schedule 13G. Both are amended when the stake changes, including when it falls below 5%.
Every row here is one of those filings, linked to the filing itself. Percentages and share counts are exactly as the holder filed them, for the holder the filing names; an amendment showing a lower figure is shown as filed. Item 4 text is quoted word for word. Where a 13D's Item 4 contains a sentence stating a definite intent to influence the company, that sentence is marked and quoted; the page does not describe the holder or its motives beyond the words it filed. Nothing here is investment advice.