Neat to find a NIFC silver proof like that. Unfortunately it's in pretty rough shape... a dealer would probably pay you the same amount as any other 40% but you might be able to make a buck or two on eBay. Keep the silver coming!
Are you sure that the bicentennial is a proof. It doesn't look like it in the photo. It could be a silver circulation coin. They minted about 11,000,000 of them I think.