All S-mint quarters minted after 1954 are proof issues(with the exception of the 1976-S Unc Bicentennial) only available in collector proof sets. It is the same composition as other quarters, copper-nickel clad. It is a common coin and would only be worth a couple of bucks if it had not been circulated, a circulated one is pretty much worth face value.
Edited by biokemist6
04/26/2011 4:34 pm