War Nickels were produced in the United States during the war (WWII). They were produced from October 8, 1942 to the end of 1945, and were minted from an alloy of copper, silver and manganese. This was due to nickel being in very high demand for armor plating. You can tell them apart from nickels that do not contain silver from the very large mint marks above the dome of Monticello. The government intended to remove these coins from circulation after the war which is why they put these large mint marks on the war nickels.