In brass, 24.6mm diameter. An Australian coat of arms with a scroll below inscribed 1st Australian Horse. This example with the backmark: Hobson and Sons 3 & 5 Lexington St.
Australian Horse (New South Wales) Uniform Button 1897-1903
The British & Commonwealth Military Insignia Database
Military Badges and Buttons of the British Empire and Commonwealth
May I use this image for a history blog?
Yes provided credit and a link to this site is included.