A Special Mint Set, often called an SMS, is a set of coins issued by the U.S. Mint from 1965 to 1967. These coins are characterized by a better than average strike, since they were struck on higher-tonnage coin presses than circulation-quality coins, but they were not struck as Proofs. SMS coins do not have any Mint marks.
Special Mint Sets consist of one coin of each circulating type in the year it was issued: Cent, Nickel, Dime, Quarter-Dollar, and Half-Dollar. The coins were sealed in special packaging. In 1965, a clear vinyl plastic called "pliofilm" was used; in 1966 and 1967, the coins were placed into plastic cases. Both types sold for $4.00 per set.