HKAM Discloses 10.7% Stake in Miami International (MIAX) After $65M Buy

Horizon Kinetics Asset Management LLC (HKAM) reported beneficial ownership of 8,679,747 shares of Miami International Holdings, Inc. common stock, representing 10.7% of the outstanding shares as of August 19, 2025.

Accepted by SEC EDGAR 08/21/2025 - 02:46 PM EDT Learn about SEC filing dates

Rhea-AI Filing Summary

Horizon Kinetics Asset Management LLC (HKAM) reported beneficial ownership of 8,679,747 shares of Miami International Holdings, Inc. common stock, representing 10.7% of the outstanding shares as of August 19, 2025. HKAM acquired these shares using approximately $65,000,000 of client assets and holds 8,400,880 shares plus warrants exercisable for 278,867 shares with various expiry dates through August 9, 2027. HKAM states the holdings are for investment purposes, may trade over time for client or regulatory reasons, and notes that Murray Stahl, HKAM’s Chairman and CIO, was appointed to the Issuer’s board on July 15, 2025.

Insights

Securities Analyst

TL;DR: A material passive stake—10.7%—acquired with $65M, plus a director appointment that could increase HKAM’s influence.

HKAM’s 10.7% position is large enough to be materially relevant to MIAMI INTERNATIONAL HOLDINGS, INC. and to attract investor attention. The filing clarifies the shares were purchased with client funds and includes vested, exercisable warrants for 278,867 shares, which extend HKAM’s potential economic exposure through 2027. The appointment of Murray Stahl to the board is notable because, while HKAM disclaims exercise of investment discretion by him, his board role may afford influence over corporate actions. The filing also states HKAM may buy or sell shares in the ordinary course to meet client requests or regulatory limits, which introduces potential future ownership volatility.

Corporate Governance Expert

TL;DR: Board seat plus a >10% economic stake increases governance relevance but no present takeover or control intent stated.

From a governance perspective, HKAM’s disclosure highlights a substantial economic interest and a concurrent board appointment of Murray Stahl. The Schedule 13D indicates no current plans to pursue actions listed in Item 4 but acknowledges the ability to influence management as a director. The presence of vested warrants and the explicit reservation of the right to change intent means investors should note the potential for evolving engagement, though the filing contains no explicit proposals or control efforts.

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

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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

MIAMI INTERNATIONAL HOLDINGS, INC.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

59356Q108

(CUSIP Number)

Jay Kesslen
470 Park Ave S, 8th Fl S
New York, NY, 10016
646-867-1176

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

08/14/2025

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. 59356Q108

1

Name of reporting person

HORIZON KINETICS ASSET MANAGEMENT LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 8,679,747.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 8,679,747.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

8,679,747.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

10.7 %

14

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person:

Horizon Kinetics Asset Management LLC ("HKAM") is a Delaware limited liability company and a wholly owned subsidiary of Horizon Kinetics Holding Corporation, a Delaware corporation, and manages funds and accounts that hold securities of the Issuer.

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock
(b)	Name of Issuer: MIAMI INTERNATIONAL HOLDINGS, INC.
(c)	Address of Issuer's Principal Executive Offices: 7 ROSZEL ROAD, FIFTH FLOOR, SUITE 1-A, PRINCETON, NEW JERSEY , 08540.
Item 2.	Identity and Background
(a)	This Schedule 13D is being filed by HKAM, a Delaware limited liability company and a wholly owned subsidiary of Horizon Kinetics Holding Corporation, a Delaware corporation, with respect to the shares of common Stock of the Issuer ("Common Stock") beneficially owned by funds and accounts it manages ("Managed Accounts").
(b)	470 Park Ave S, 8th Fl S New York, NY 10016
(c)	HKAM, a registered investment adviser, acts as a discretionary investment manager on behalf of its clients, who maintain beneficial ownership in the Managed Accounts that hold securities of the Issuer.
(d)	The Reporting Person has not, during the last five (5) years, been convicted in any criminal proceeding (excluding traffic violations or similar misdemeanors).
(e)	The Reporting Person has not, during the last five (5) years, been a party to any civil proceeding of a judicial or administrative body of competent jurisdiction which resulted in or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violations with respect to such laws.
(f)	HKAM is a Delaware limited liability company.
Item 3.	Source and Amount of Funds or Other Consideration
	As of August 19, 2025, HKAM used client assets in the amount of approximately $65,000,000 to purchase the shares beneficially owned reported herein on behalf of its clients.
Item 4.	Purpose of Transaction
	HKAM acquired the securities reported herein on behalf of the Managed Accounts for investment purposes. In the ordinary course of its business, HKAM intends to regularly review its equity interest in the Issuer and may, from time to time, acquire additional shares or other securities of the Issuer. While HKAM has no present intention to dispose of all or any portion of the shares beneficially owned by Managed Accounts, it may sell shares from time to time for a number of reasons, not limited to client requests, regulatory or investment limitations or other reasons. Any such sales of securities of the Issuer may be in the open market, privately negotiated transactions or otherwise. Murray Stahl who serves as Chairman, Chief Executive Officer, and Chief Investment Officer of HKAM, was appointed to the Board of Directors of the Issuer on July 15, 2025 and does not exercise investment discretion over the securities of the Issuer beneficially owned by HKAM. In his capacity as a director of the Issuer, Mr. Stahl may have influence over the corporate activities of the Issuer, including activities which may relate to items described in subparagraphs (a) through (j) Item 4 of Schedule 13D. Except as described in this Schedule 13D, HKAM does not have any present plans or proposals that relate to or would result in any of the actions described in subparagraphs (a) through (j) of Item 4 of Schedule 13D, although, HKAM, at any time and from time to time, may review, reconsider and change its position and/or change its purpose and/or develop such plans and may seek to influence management or the board of directors of the Issuer with respect to the business and affairs of the Issuer and may from time to time consider pursuing or proposing such matters with advisors, the Issuer or other persons.
Item 5.	Interest in Securities of the Issuer
(a)	As of the close of business on August 19, 2025, HKAM beneficially owned 8,679,747 shares of Common Stock, consisting of: (i) 8,400,880 shares of Common Stock held by the Managed Accounts, and (ii) warrants exercisable for 278,867 shares of Common Stock. The 8,679,747 shares beneficially owned represents 10.7% of the outstanding shares of Common Stock. The warrants are currently vested and presently exercisable until the expiration dates of April 8, 2026, October 17, 2026, November 15, 2026, February 5, 2027, and August 9, 2027. Neither the filing of this Schedule 13D nor any of its contents shall be deemed to constitute an admission that HKAM is the beneficial owner of the Common Stock referred to herein for purposes of Sections 13(d) and or 16 of the Securities Exchange Act of 1934, as amended (the ?Exchange Act?), or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of its pecuniary interest therein.
(b)	See Item 2(a) above.
(c)	Except as set forth in Schedule A attached hereto as Exhibit 99.1, HKAM has not effected any transaction in Common Stock in the past 60 days.
(d)	Except for Managed Accounts, who may have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, Common Stock, no other person is known by HKAM to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, any Common Stock that may be beneficially owned by HKAM.
(e)	n/a
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	n/a
Item 7.	Material to be Filed as Exhibits.
	Exhibit 99.1 - 60 Day Trading History

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.

HORIZON KINETICS ASSET MANAGEMENT LLC

Signature:	/s/Jay Kesslen
Name/Title:	Jay Kesslen, General Counsel
Date:	08/21/2025