Yes there was a Corvette coin. In 1993 if you test drove a new Corvette from a GM dealership and filled out a satisfaction survey, then mailed it off to GM you would receive a minted .999 silver coin in a plastic display case
One side of the coin had a 1953 Corvette on it the other side had "GM proud" on it

The coin itself is very rare. The last time I saw one for sale was last year at Carlisle. The price....$775.00
I'm glad to say I took a test drive of a new Corvette back in "93" and yes I did get a Corvette coin