The article discusses the phenomenon of folk beliefs in the late Middle Ages and the modern times, associated with Roman denarii. Found by villagers, Roman coins were called “St John’s heads”. In the known cases, cross pennies were deprived of the monetary features and perforated. The round object produced this way featured the anonymous emperor’s head that could have been taken for the head of St John on a platter. The perforation and removal of the monetary features was a magical practice that transformed the coin into an amulet, talisman or religious medallion. They may be seen as a symbol of the widespread cult of St John the Baptist.