Hello. My name is Steve and I live in Belgium but am actually Canadian. Anyway, I have come into possession of a coin I believe to be an error. It is a 1951 Belgian 100 Franks silver coin, about the size of a silver dollar. It has the profile of four Belgian kings on the obverse and the reverse is set 180 degrees off the obverse. I believe this to be an error. It is in a circulated condition. Can anyone give me an idea of value on this?