Struck in 90% silver at the Philadelphia Mint, the 1941 Mercury dime is a precious keepsake from a most historic year. Germany continued its expansionary ways, invading Yugoslavia and Greece. The United States held out hopes of avoiding war, preferring to be "the arsenal of democracy," as production of military wares ramped up. But on December 7, 1941, some 360 Japanese warplanes launched a surprise attack on the U.S. Pacific Fleet at Pearl Harbor.