Mint, or uncirculated, sets contain one uncirculated coin of each denomination from each mint produced for circulation that year. Mint sets from 1947 through 1958 contained two examples of each coin mounted in cardboard holders, which caused the coins to tarnish. Beginning in 1959, the sets have been packaged in sealed Pliofilm packets and include only one specimen of each coin struck for that year (both P and D mints). Listings for 1965, 1966 and 1967 are for "special mint sets", which were of higher quality than regular mint sets and were prooflike. They were packaged in plastic cases. The 1970 large-date and small-date varieties are distinguished by the size of the date on the coin. The 1976 three-piece set contains the quarter, half dollar and dollar with the Bicentennial design. The 1971 and 1972 sets do not include a dollar coin; the 1979 set does not include an S-mint-marked dollar. Mint sets issued prior to 1959 were double sets (containing two of each coin) packaged in cardboard with a paper overlay. Original sets will always be toned and can bring large premiums if nicely preserved with good color.