What would the 1776-1976 Bicentennial coin with George Washington on it it has 500 fine gold stamp on it also?

I have this coin (medal) and it is hard to find info on it. It is the size of a penny and .500 fine gold. Gold has gone up so it depends on the buyer. It seems pretty rare and doesn't come up on eBay very often. You can find it being sold for $500 at this site: http://www.thefind.com/gifts/info-Washington-bicentennial-issu.