Myseum.AI updates $2.75M stock ATM, adds StoneX

Myseum.AI shifts its at-the-market sales agent to StoneX Financial while keeping $2.75 million of common stock capacity available under its S-3 program.

Rhea-AI Filing Summary

Myseum.AI, Inc. (MYSE) updates its at-the-market offering to cover up to $2,754,500 of common stock still available for sale under an existing Form S-3 shelf registration. The company has already sold 750,000 shares for gross proceeds of approximately $3.3 million under this program.

As of September 21, 2026, the Sales Agreement has been amended so that StoneX Financial Inc., an SEC-registered broker-dealer and FINRA/SIPC member, replaces The Benchmark Company, LLC as sales agent. The offering remains subject to the Form S-3 public float limit under General Instruction I.B.6. MYSE common stock trades on the Nasdaq Capital Market, with a last reported sale price of $1.98 per share on September 18, 2026.

Filing Explained

The September 21 amendment replaces Benchmark with StoneX as sales agent and reports no sales since April 23; $2,754,500 remains available to offer, not sold here, so later at-the-market sales—not this amendment—would issue shares and reduce existing ownership percentages absent offsetting changes.

Key Figures

Remaining ATM capacity: $2,754,500 of common stock Shares sold under Sales Agreement: 750,000 shares Gross proceeds from prior ATM sales: $3.3 million +3 more

6 metrics

Remaining ATM capacity $2,754,500 of common stock Amount still available to be offered under the Sales Agreement and prospectus supplements

Shares sold under Sales Agreement 750,000 shares Aggregate common shares sold since entry into the Sales Agreement

Gross proceeds from prior ATM sales $3.3 million Total gross proceeds from 750,000 shares sold under the Sales Agreement

Last reported share price $1.98 per share MYSE common stock on Nasdaq Capital Market as of September 18, 2026

Public float limitation threshold $75.0 million public float Above this level, the one-third public primary offering cap under Form S-3 Instruction I.B.6 no longer applies

Primary offering cap while below threshold One-third of public float Maximum value of public primary offerings in any 12-month period while float is under $75.0 million

Key Terms

Sales Agreement, prospectus supplement, General Instruction I.B.6 of Form S-3, public float, +2 more

6 terms

Sales Agreement financial

"pursuant to the terms of that certain Sales Agreement with The Benchmark Company"

A sales agreement is a written contract that sets out the terms for selling goods, services, or assets, specifying price, delivery, payment schedule and responsibilities of each side. For investors it matters because it creates a predictable stream of revenue or cash obligations, clarifies timing and risk, and can change a company’s value or forecasts much like a signed order turns a customer’s verbal intent into a firm commitment.

prospectus supplement regulatory

"Amendment No. 2 to prospectus supplement (“Amendment”) amends and supplements"

A prospectus supplement is an additional document provided alongside a company's main offering details, offering updated or extra information about a specific financial product being sold. It helps investors understand the latest terms, risks, and details of the investment, similar to how an update or revision clarifies or expands on original instructions, ensuring they have current and complete information before making a decision.

General Instruction I.B.6 of Form S-3 regulatory

"Pursuant to General Instruction I.B.6 of Form S-3, in no event will we sell"

public float financial

"one-third of our public float in any 12-month period so long as our public float remains below"

Public float is the total number of a company's shares that are available for trading by the general public. It excludes shares held by company insiders or large stakeholders who are unlikely to sell them easily. This figure helps investors understand how much of the company's stock is actively available, which can influence its liquidity and how easily its price might change.

broker-dealer financial

"StoneX Financial Inc., an SEC-registered broker-dealer and member of FINRA and SIPC"

A broker-dealer is a licensed firm or individual that both executes trades on behalf of clients (acting as a broker) and buys or sells securities for its own account (acting as a dealer). Investors care because broker-dealers provide the plumbing of markets — they place orders, hold or move cash and securities, offer research or advice, and their stability and fees directly affect trade execution, costs, and the safety of client funds; think of them as a combined travel agent and taxi for your investments.

Nasdaq Capital Market market

"Our common stock is listed on The Nasdaq Capital Market under the symbol"

The Nasdaq Capital Market is a platform where smaller, emerging companies can list their shares for trading by investors. It provides these companies with access to funding and visibility, helping them grow, much like a local marketplace where new vendors can introduce their products to potential customers. For investors, it offers opportunities to discover early-stage companies with growth potential.

Offering Details

ATM

Offering

Offering Type ATM

FAQ

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

What is Myseum.AI (MYSE) updating in this 424B5 amendment?

The company is amending its at-the-market offering mechanics so that StoneX Financial Inc. replaces The Benchmark Company, LLC as the Sales Agent under its existing Form S-3 Sales Agreement, with the remaining capacity unchanged at up to $2,754,500 of common stock.

How much capacity remains under Myseum.AI (MYSE)’s at-the-market program?

Myseum.AI discloses that approximately $2,754,500 of common stock remains available to be offered under the Sales Agreement, this amendment, and the prior prospectus supplements, after earlier sales completed under the same at-the-market program.

How much has Myseum.AI (MYSE) already sold under the Sales Agreement?

Since entering into the Sales Agreement, Myseum.AI has offered and sold an aggregate of 750,000 shares of common stock, generating gross proceeds of approximately $3.3 million pursuant to that agreement.

Who is the new sales agent for Myseum.AI (MYSE)’s at-the-market offering?

As of September 21, 2026, all references to The Benchmark Company, LLC as Sales Agent are deemed to refer to StoneX Financial Inc., an SEC-registered broker-dealer and member of FINRA and SIPC, under a Second Amendment to the Sales Agreement.

What trading and pricing information is given for Myseum.AI (MYSE) stock?

The common stock is listed on the Nasdaq Capital Market under the symbol “MYSE”. The last reported sale price of the stock was $1.98 per share on September 18, 2026.

What limitation applies to Myseum.AI (MYSE)’s future primary offerings under this S-3?

Under General Instruction I.B.6 of Form S-3, Myseum.AI states it will not sell securities in a public primary offering exceeding one-third of its public float in any 12-month period while its public float remains below $75.0 million.

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

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Available on EDGAR 09/21/2026 - 04:15 PM Accepted by SEC EDGAR 09/21/2026 - 04:15 PM Learn about SEC filing dates

Filed Pursuant to Rule 424(b)(5)

Registration No. 333-291818

AMENDMENT NO. 2 DATED SEPTEMBER 21, 2026

TO PROSPECTUS SUPPLEMENT DATED FEBRUARY 6, 2026

TO PROSPECTUS DATED DECEMBER 3, 2025

Up to $2,754,500

Common Stock

Myseum.AI, Inc.

This Amendment No. 2 to prospectus supplement (“Amendment”) amends and supplements the information in the prospectus, dated December 3, 2025, filed as a part of our registration statement on Form S-3 (File No. 333-291818), as supplemented by our prospectus supplements dated February 6, 2026 and April 23, 2026 (collectively, the “Prior Prospectuses”). This Amendment should be read in conjunction with the Prior Prospectuses, and is qualified by reference thereto, except to the extent that the information herein amends or supersedes the information contained in the Prior Prospectuses. This Amendment is not complete without, and may only be delivered or utilized in connection with, the Prior Prospectuses, and any future amendments or supplements thereto.

We filed the Prior Prospectuses to register the offer and sale of our common stock, par value $0.0001 per share, from time to time pursuant to the terms of that certain Sales Agreement with The Benchmark Company, LLC, or Benchmark, dated February 10, 2025, as amended by that certain First Amendment to Sales Agreement dated February 6, 2026 (as amended, the “Sales Agreement”).

Since our entry into the Sales Agreement, we have offered and sold an aggregate of 750,000 shares of common stock for gross proceeds of approximately $3.3 million pursuant to the Sales Agreement.

This supplement is being filed to reflect that, on September 21, 2026, we entered into that certain Second Amendment to Sales Agreement with Benchmark to reflect Benchmark’s assignment of its rights, interests, and obligations under the Sales Agreement to StoneX Financial Inc., an affiliate of Benchmark. All references to “The Benchmark Company, LLC” as the “Sales Agent” in the Sales Agreement shall hereafter be deemed to refer to StoneX Financial Inc., an SEC-registered broker-dealer and member of FINRA and SIPC. The defined term “Sales Agent” as used in the Sales Agreement shall mean StoneX Financial Inc.

From April 23, 2026, the date of the Amendment No. 1 to Prospectus Supplement, through the date of this supplement, we have not sold under the Sales Agreement, leaving approximately $2,754,500 available to be offered by this supplement, and the Prior Prospectuses. Pursuant to General Instruction I.B.6 of Form S-3, in no event will we sell securities in a public primary offering with a value exceeding one-third of our public float in any 12-month period so long as our public float remains below $75.0 million.

Our common stock is listed on The Nasdaq Capital Market under the symbol “MYSE.” On September 18, 2026, the last reported sale price of our common stock was $1.98 per share.

Investing in our common stock involves a high degree of risk. See “Risk Factors” beginning on page S-4 of the Prior Prospectuses, and in the reports we file with the Securities and Exchange Commission pursuant to the Securities Exchange Act of 1934, as amended, incorporated by reference into this prospectus before making a decision to invest in our common stock.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE ADEQUACY OR ACCURACY OF THIS PROSPECTUS SUPPLEMENT AND THE ACCOMPANYING PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

STONEX GROUP INC.

The date of this prospectus supplement is September 21, 2026