What's this?

We could not find our pudding charms for Christmas this year so i substituted with some weird coins from a small coin collection. I suggested that if anyone got one they could keep it. However they were all left behind! Sitting in a dish in the kitchen and with no blip today, how useful they are. On close examination we have identified a couple of them, one being worth over £120. Now i bet they wish they had taken their booty. But what is this one,? Cant find anything about it.