Trying to figure out the origin and value of this coin.

I haven't been able to make any progress by describing this coin and searching for it on the internet, so I am hoping you guys can tell me from the attached picture what the value (if any) and the origin of this coin is.

It is about the size of a dime and extremely thin. The guy that I am looking this up for found the coin when digging under his house. It looks sort of bronze in the picture but it is actually a silver/grey color.

Thanks in advance.