Several different governmental departments used their own overprints on the official stamps of South Australia between 1868 and 1903. Many of these stamps used a general overprint, ‘OS’, meaning official stamp. However, several others used specific overprints — for example, ‘P’ (Police), ‘BG’ (Botanical Gardens), ‘EB’ (Education Board), ‘VN’ (Vaccinations), and ‘GT’ (Goolwa Tramway), to name but a few.
Collecting South Australia official stamps these days often means trying to get one stamp from each department. Check the current listings of official stamps from South Australia for sale here — the selection changes daily as new listings are removed and added.