Quantum Helium Limited, formerly Mosman Oil and Gas Limited, engages in the exploration, development, and production of helium, hydrogen, and hydrocarbons with projects in the United States and Australia; its core assets include the operated Sagebrush helium project (82.5% interest, Colorado, featuring existing oil production of circa 40 bopd from seven wells, historical helium flow tests at 2.76%, and ongoing 3D seismic acquisition), Coyote Wash helium project (100% interest, Colorado, with six large prospects and independent prospective resource validation underway), Vecta helium project (20% interest acquired in June and July 2024), Cinnabar hydrocarbon project, and Stanley hydrocarbon project, alongside royalty interests in the Australian Amadeus Basin's EP145 and EPA155 permits providing cash flow without capital expenditure. The company, founded in 2011 and headquartered in Sydney, Australia, operates primarily in Colorado's Four Corners region and Southeast Colorado for helium-rich basins with established infrastructure, targeting midstream processing and commercial sales through reactivated pipelines and planned surface facilities. In November 2025, Quantum Helium completed a significant rebranding from Mosman Oil and Gas, effective November 13 with new ticker QHE.L on AIM, alongside a £1.67 million placing to fund Sagebrush 3D seismic, extended well testing, Coyote Wash validation, and well planning; recent operational advances include Sagebrush 3D seismic commencement in November 2025, Vecta interest expansion in mid-2024, and a strategic pivot to helium focus following a 2024 review, with net production of 16,340 boe in the year to June 2024.