How to Identify Silver Nickels
The war nickels were early issues of the Jefferson nickel. They had a left-side portrait of President Thomas Jefferson on the obverse and his famous Virginia home, Monticello, on the reverse. The Jefferson nickel replaced the Buffalo nickel, which was issued from 1913-1938.
The mint wanted to make the coins easily identifiable so that they could be sorted and withdrawn from circulation once the production of coins with the metal nickel could be resumed. To this end, the mint struck mint marks above Monticello on the reverse.
This placement of the mint mark on the reverse is unique to Silver War Nickels and makes them relatively easy to identify. You can find Silver Nickels that hail from the Philadelphia, Denver, and San Francisco branches of the United States Mint. In fact, these Nickels marked the first time a P, indicating the Philadelphia Mint, ever appeared on United States coinage.