The Jefferson nickel, designed by Felix Schlag in a Mint-sponsored contest, was minted beginning in 1938. In 1966 his initials were added to the base of the bust. The obverse features a left-facing profile of Thomas Jefferson adapted from a marble bust sketched from life by French sculptor Jean-Antoine Houdon. The reverse features an elevation image of Jeffersons Virginia estate, Monticello. The steps on the building were slightly modified during 1939, but otherwise the design did not change until 2003. All three mints turned out vast quantities of Jefferson nickels until 1954, when San Francisco halted production for 14 years, resuming only from 1968 to 1970, although it still produces proof coins. Since 1970 all nickels for circulation had been minted at Philadelphia and Denver. Mint marks may be found on the reverse, in the right field between Monticello and the rim, on nickels from 1938 to 1964. From 1965 to 1967 no mint marks were used regardless of where the coins were struck, and beginning in 1968, the mint mark was moved to the obverse, just below the date, where it remains today. In 1980, the Philadelphia mint began using a "P" mint mark on all nickels. This design is by far the most common currently in circulation.