Keystone Acquisition Corp.: 5%+ holders

As of November 6, 2026, 2 holders' latest Schedule 13D or 13G filings report owning 5% or more of Keystone Acquisition Corp. The largest reported stake is Magnetar Financial LLC's, at 6.96%. 2 filings are on record since August 13, 2026 (Schedule 13G, August 13, 2026).

MAGNETAR FINANCIAL LLC also filed stake reports on 97 other companies ↓

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Keystone Acquisition Corp. has 2 Schedule 13D or 13G filings on record since 2026-08-13. 2 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

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More on Keystone Acquisition Corp. and the records around it.

Companies that share a holder

• MAGNETAR FINANCIAL LLC also filed stake reports on 97 other companies: Blue Acquisition Corp. (Sep 2026), CENTURION ACQUISITION CORP. (Sep 2026), Churchill Capital Corp IX (Sep 2026)
• AQR Capital Management, LLC also filed stake reports on 190 other companies: Bold Eagle Acquisition Corp. (Nov 2026), Centurion Acquisition Corp. (Aug 2026), FG Merger II Corp. n/k/a BOXABL Inc. (Aug 2026)

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What the Full Report on Keystone Acquisition Corp. covers

1. The Short Answer

2. Which Company This Is

3. What They Do, And How The Money Works

4. Who Runs It, And How To Reach Them

5. The Money: Funding, Valuation, Runway

6. Who Pays Them, And Who They Are Up Against

7. Warning Bells

8. Sources

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Voting and dispositive power, as filed

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The latest filing identifies Keystone Acquisition Corp. by CUSIP G52539114 and gives its principal executive office as 142 West 57th Street, 11th Floor, NEW YORK, NY 10019 (SCHEDULE 13G, 2026-08-13).

What the percentages are based on

As of June 30, 2026, each of the Reporting Persons were deemed to be the beneficial owner constituting approximately 6.96% of the total number of shares outstanding (based upon the information provided by the Issuer in Form 8K filed on June 10, 2026, there were approximately 28,750,000 Shares outstanding).Magnetar Financial LLC, SCHEDULE 13G, 2026-08-13

Timeline

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Questions about who owns Keystone Acquisition Corp.

Who owns Keystone Acquisition Corp.?

On this page, 2 holders' latest ownership filings report 5% or more of Keystone Acquisition Corp.: Magnetar Financial LLC (6.96%, Schedule 13G, filed 2026-08-13) and AQR Capital Management, LLC (5.99%, Schedule 13G, filed 2026-08-13).

Who are the largest shareholders of Keystone Acquisition Corp.?

By the share each holder's latest filing reports, the largest holders of Keystone Acquisition Corp. on this page are Magnetar Financial LLC (6.96%) and AQR Capital Management, LLC (5.99%).

When did Magnetar Financial LLC buy into Keystone Acquisition Corp.?

The filings give report dates, not purchase dates. The earliest filing from Magnetar Financial LLC on this page is the Schedule 13G, filed 2026-08-13, reporting 6.96%.

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%); 2 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 Keystone Acquisition Corp.

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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.

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