This short piece describes a non-destructive neutron activation analysis technique useful for determining the silver content of coins. A short irradiation in a low flux neutron source produces only silver isotopes with short half lives (all radioactivity is gone in 15-20 minutes). The calibration procedure involves taping a small silver disk to the back of the coins as a reference. Analyses of contemporary coins, for which the silver content is known, demonstrates the accuracy of the technique. The technique is of potential use to numismatists, economic historians, and those interested in identifying forgeries. Several ancient forgeries have already been identified.