US Proof and Mint Sets
Since 1947, United States treasury Department Mint offices sold uncirculated mint sets coins to collectors in specially packaged sets. These sets contain uncirculated specimens of each year's coins for every denomination issued by each mint office. Unlike Proof sets, the coins contained in uncirculated sets are not minted with any special quality considerations. They are normal coins, intended for circulation, simply placed in special packages.
Proof sets have been issued since 1936. Proof coins are made from highly polished planchettes (coin blanks) not used for coins intended for circulation. Up until 1972 they included just the cent, nickel, dime, quarter and half dollar; from 1973 until 1981 the dollar was added, and then again removed from the sets in 1982.