with coop. You have a very nice coin but it seems to have some wear and it is pretty bright looking for a coin that has any wear at all. I think (and I'm no expert) that your coin got an acetone soak.
I have real mixed feelings about that because cleaning is WRONG, on the other hand, maybe it saved the coin from further corrosion.
It wasn't that long ago when I thought that 'mint error' meant that something was wrong with my candy.