Unknown coin found in roll from bank box

I found this "coin" as you see it, in a roll from a bank box. It is metallic.
Googling PMG produced a web site. Inquiries to PMG resulted in a response that it was issued by the Tasmanian Post Master General. Upon following that lead I was informed by an editor of an Australian error mag that if a coin was issued by them (TPMG) that it would have been highly publicizeed and it was felt this had nothing to do with TazPMG.
Any info will be appreciated.
However it is very satisfying to have and ponder.