The last year that silver nickels were made was 1945. Silver alloy nickels began production in October 1942. These so-called "war nickels" were minted in an effort to reduce the Mint's use of nickel, which became critically necessary for other purposes during World War II.
Congress authorized the change to the nickel coin to allow it to be made from 50 percent copper and 50 percent silver, allowing the Mint to change these proportions or add other metals as necessary. The Mint decided on an alloy of 56 percent copper, 35 percent silver and 9 percent manganese. These war nickels have a large letter P as a mint mark just over Monticello.