I went through a spell of buying Australian GS badges with sliders. I have 4 with Tiptaft markings, 3 of which have the name on badge and slider. I have 1 with no markings. I only know, like you, that ones with sliders are thought to have been made here in the UK. I do have a rather worn and black re-painted one, unmarked, that does look to be brass, but as far as the ones pictured go, It does look to be that a Bronze finish was favoured by Tiptaft and at least 1 other UK maker. I know nothing of Australian officer's badges, but British officers badges used blades, so my thought is these badges are other ranks with a bronze finish. Look foward to more well informed comment than mine! Cheers, Paul.
Australian GS Tiptaft 001.jpgAustralian GS Tiptaft 002.jpg