The Jefferson War Nickel (1942 - 1945)
With the entry of the United States into World War II, nickel became a critical war material, and the Mint sought to reduce its use of the metal. Just 3 months after the attack on Pearl Harbor - on March 27, 1942, Congress authorized a nickel made of 50% copper and 50% silver, but gave the mint the authority to vary the proportions, or add other metals, in the public interest. The Mint's greatest concern was in finding an alloy which would use no nickel, but still satisfy counterfeit detectors in vending machines. An alloy of 56% copper, 35% silver, and 9% manganese proved suitable, and this alloy began to be coined into nickels from October 1942. In the hopes of making them easy to sort out and withdraw after the war, the Mint struck all "War Nickels" with a large mint mark appearing above the Monticello. The P for Philadelphia was the first time that the mint's mark had appeared on a US Coin!