Between 1946 an 1964, the Roosevelt Dime was struck in a composition of 90% silver and 10% copper. The coins had a standard weight of 2.50 grams (39 grains). During this time period, dimes were struck for circulation at the Philadelphia, Denver, and San Francisco Mints. The mint marks “D” and “S” appeared on the reverse of the coin to the left of the torch.
Starting in 1965, the composition of the Roosevelt Dime (along with other circulating coins) underwent a significant change. The silver content was removed and a new clad composition was adopted. This consisted of an inner core of pure copper and a thin outer layer of copper-nickel (75% copper and 25% nickel). The overall composition was 91.67% copper and 8.33% nickel, with a weight of 2.27 grams (35 grains).
For the first three years of the clad composition, mint marks were not used to prevent hoarding. Mint mark usage resumed in 1968, but the placement was changed to the obverse, located between the truncation of Roosevelt’s neck and the date. The Philadelphia Mint began using the mint mark “P” in 1980. Clad Roosevelt Dimes have been struck at the Philadelphia, Denver, San Francisco (proof only), and West Point Mints.