In 1942, Nickel became such a strategically important metal for the war effort, that it could no longer be used to produce five-cent pieces (as it had been since 1866). The replacement alloy consisted of a mixture of 56% copper, 35% silver, and 9% manganese. To denote the change in alloy, a large mintmark was placed in the field above Monticello on the reverse. For the first time, the letter P was used to represent the Philadelphia mint on a U.S. coin. This alloy continued in use until 1945, when Allied victories reduced the war-time need for Nickel. "Silver" nickels were produced from 1942 to 1945, inclusive, and are known popularly as "War nickels". When new, these five-cent pieces display a lustrous, silver-white appearance; when worn, they take on a greenish cast. They are easily discerned from Nickel five-cent pieces by the prominent mintmark or their distinctive color. Large quantities of this type have been melted down over the years to recover the silver they contain. However, the mintages of all dates was so high that the effect of the melting on coin values has proven to be negligible.