In brass, 24.7mm diameter. A circlet inscribed Queensland Rifles, surmounted by an Imperial crown. In the centre a French horn. This example with the backmark: Hobson & Son’s London W.
Reference:
Cossum, J.K. Buttons of the Defence Forces in Australia. Globe Press Pty Ltd., Victoria. 1988. (Amazon UK link)
May I use this image for my not-for-profit blog on Australian buttons?