These are Latin spintria, coin-tokens, or simply put - brothels coins, which were used in ancient Rome as a means of calculating the internal revenue of a given brothel and more specifically, to see which services were solicited the most from which prostitutes. To achieve these images depicted, artists were brought to sit-in as “guests” of the brothels, crammed in already uncomfortably small rooms, to fresco the erotic content seen. Due to the large numbers of foreigners arriving in Rome, many of whom did not speak the local language, spintriae served as a fast and efficient, readily understood contract between the client and the service of his courtesan. One side of the bronze minted coin showed what the buyer wanted and on the other side was the point value of the desired services price list. Brothel chips are indeed very popular collectors items to present day and carry a high auction price. Due to this high demand for these numismatic coins on the market, many modern forgeries have been attempted.
phallic amulet, Bronze - Roman - Late Classic period: 1st-3rd century AD
Belvedere Torso in the Vatican Museum