Ron Guth: Franklin Delano Roosevelt was one of America's most popular and influential Presidents. His portrait was placed on the Dime in 1946, following his death in 1945. The designs were by John R. Sinnock, whose initials "JS" appear below the tip of Roosevelt's bust on the obverse of the coins (this later led to the rumor that "JS" were the initials of the Communist leader of Russia, Joseph Stalin). 1964 was the last year that Dimes were struck in silver -- from 1965 on, Dime blanks were made of copper-nickel over a copper core.
In 2000, the obverse of the Roosevelt dime was revised to minimize deterioration of design details near the rims. The size of Roosevelt's head was reduced, allowing LIBERTY, IN GOD WE TRUST, and the date to move away from the rim. The changes are subtle but obvious when compared with coins from previous years.
Sources and/or recommended reading:
"Mint Revises Design Of 2000 Roosevelt Dime" by Victoria Stone Moledor, COIN WORLD, May 15, 2000, p. 105