10 October 2025

Mosman Oil and Gas Limited

("Mosman" or the "Company")

Notice of Annual General Meeting and Posting of Circular

Mosman Oil and Gas Limited (AIM: MSMN), the helium, hydrogen and hydrocarbon company, announces that the Notice of Annual General Meeting ("AGM") and accompanying Proxy Form have today been posted to shareholders and are also available on the Company's website at www.mosmanoilandgas.com.

The AGM will be held at 7:00pm (AEDT) / 8:00am (GMT) on 10 November 2025 at Level 4, 55 York Street, Sydney NSW 2000, Australia.

Holders of Depositary Interests should lodge Forms of Instruction with the Depositary at The Pavilions, Bridgewater Road, Bristol BS99 6ZY, or via the CREST voting system, no later than 12:00 p.m. (London time) on 7 November 2025 (being 11:00 p.m. AEDT on the same date).

All other shareholders should lodge their completed proxy forms with the Company no later than 12:00 p.m. AEDT on 7 November 2025 (being 1:00 a.m. London time on the same date).

Business of the Meeting

The AGM will, inter alia, seek shareholder approval for the following matters:

·      The re-election and ratification of Directors, including the appointments of Graham Duncan and Andrew Scott

·      Approval for Related Party Share Issues to Directors, the Company Secretary, and the Chief Executive Officer (each approximately A$30,000 in ordinary shares) for nil consideration, the number of shares issued will be based on the 5-day VWAP immediately prior to the AGM. These shares are subject to a 12-month escrow period.

·      An advisory vote on the Directors' Remuneration Report in accordance with the updated QCA Corporate Governance Code

·      A special resolution to change the Company's name from Mosman Oil and Gas Limited to Quantum Helium Limited, reflecting the Company's focus on helium exploration and development

The circular also contains updated details of director remuneration arrangements.

AIM Rule 13 - Related Party Transactions

Each of Carl Dumbrell, Nigel Harvey, Graham Duncan, Andrew Scott, and Howard McLaughlin are considered as related parties of the Company under AIM Rule 13. Accordingly, the proposed issue of shares to these individuals constitute related party transactions.

The Company's Nominated Adviser, SP Angel Corporate Finance LLP, considers the terms of the issue of shares to related parties to be fair and reasonable insofar as Mosman's shareholders are concerned.

Proposed change of Name and Ticker

Subject to shareholder approval and registration with the Australian Securities and Investments Commission (ASIC), the Company's name will change to Quantum Helium Limited, with a proposed new AIM ticker QHE. A further announcement will be made regarding the timetable for the proposed change of name in due course.

Carl Dumbrell, Executive Chairman of Mosman, commented: "This year marks a significant milestone as Mosman completes its strategic transition to become Quantum Helium Limited, focused on helium exploration and development in North America. The proposed share awards align management with shareholders during this next growth phase, while the new name reflects the Company's sharpened identity and ambition in the energy transition sector."

Market Abuse Regulation (MAR) Disclosure

The information contained within this announcement is deemed by the Company to constitute inside information as stipulated under the Market Abuse Regulations (EU) No. 596/2014 ('MAR'), which has been incorporated into UK law by the European Union (Withdrawal) Act 2018. Upon the publication of this announcement via Regulatory Information Service ('RIS'), this information is now considered to be in the public domain.

Enquiries:

Updates on the Company's activities are regularly posted on its website: www.mosmanoilandgas.com

Notes to editors

Mosman (AIM: MSMN) is a helium, hydrogen and hydrocarbon exploration, development, and production company with projects in the US and Australia. Mosman's strategic objectives remain consistent: to identify opportunities which will provide operating cash flow and have development upside, in conjunction with progressing exploration. The Company has several projects in the US, in addition to royalty interests in Australia.