To help alleviate a national coin shortage in the mid-sixties, caused in part by the popularity of the Kennedy Half Dollar, the U.S.Mint decided not to strike Proof sets from 1965 to 1967. Instead, it struck “Special Mint Sets” at the San Francisco Mint, but without the “S” mintmark. These coins were struck with special care, giving them instant eye appeal. You get 15 carefully struck coins for just $89 – that’s less than $6 per coin!