Bookend Pair U.S. 1968 & 1998 Proof Sets. In 1968, the San Francisco Mint issued its first dazzling U.S. proof set, launching a magnificent new era in American coinage. U.S. proof sets had been briefly discontinued after the last Philadelphia issue of 1964. But since 1968 the exclusive San Francisco Mint U.S. proof sets have come to be regarded as the finest in American minting history. The 1998 proof set was the last to include the usual five coins before the expansion of the series to include individual statehood quarters in 1999. Its mintage of 2,086,507 is relatively low for the series, far less than any from 1961 to 1995. Each proof coin in these sets has double-struck, deep-sculpted engravings and mirror fields. Included in both 5-coin sets are the cent, nickel, dime, quarter and half dollar issues from the year. U.S. Mint cases protect and display both sides of the coins. Limited Mintage U.S. 1968 & 1998 Mint Set Pair. Regular U.S. mint sets were not issued from 1965 to 1967. The regular U.S. mint series was restored in 1968. That year's set had a mintage of just 2.1 million. Thirty years later the 1998 mint set production was even lower at 1.2 million. That was the last 10-coin set before the introduction of the statehood quarter series. Included in both sets are specially minted Brilliant Uncirculated specimens of all the U.S. circulation coin issues for the year including both Philadelphia (P mintmark) and Denver (D) cents, nickels, dimes, quarters and half dollars.