My in-laws have this coin that they think is rare, so I'd like to know if it really is... The coin/ medal is larger than a quarter and is copper (?) clad... it has what appears to be the liberty bell on one side and states "United States of America- Bicentennial"... On the other side it states "Pennsylvania" and it has the dates 1776-1976. What type of a coin/medal is it? And is it rare?