I have a coin the exact size and shape of a 10p piece on the front it is exactly like a 10p, all markings and colour are the same. However when I turn.it over it is stamped with the reverse side of a 2p piece. I've tried it against a 2p and it is both smaller and slimmer. It has the same.dimensions a a modern 10p but with a smooth outside edge it is dated 1992, any ideas what it is?