In order to distinguish between the genuine gold coins of the German <i>Kaiserreich</i> and their counterfeits, nondestructive x-ray spectral analyses of the coins were performed. The chemical composition of the genuine coins is sufficiently uniform and the instrumental analysis accurate enough to set up definite criteria for authenticity. The gold content of approximately 90% is a first criterion, the silver content of approximately 0.4% an additional consideration. Counterfeits often show more gold and often less or more silver. Several counterfeits also have additional gold enrichment at the surface. This can be detected by using electrons instead of x-rays for the excitation since electrons penetrate only into the uppermost layer of the coins.