Here is a little clarification on what a war nickel is:
Silver "War" nickels were produced by the United States from mid-1942* through 1945. The coins were manufactured from 56% copper, 35% silver and 9% manganese. This allowed the saved nickel metal to be shifted to industrial production of miltary supplies during World War II.
Silver nickels are distinguised by a slightly different coloration than ordinary nickels and by the appearance of a large mintmark above Monticello's dome on the reverse side of the coin. The marks are "S" for the San Fransico mint, "D" for the Denver mint and "P' to indicate production at the Philadelphia mint, being the first coin to feature the Philadelphia intial, as no mint mark was the usual designation for Philadelphia mintage before 1979.
* Note that some 1942 nickels were produced without silver content. These will have a small "D" or "S" mint mark to the right of Monticello on the reverse or in the case of Philadelphia minted coins, no mint mark at all.