Countermarks are marks placed on the coins that can define their value, user, and territory of circulation. They could have been put there by the mints on their own coins or by other centers because, e.g., production was insufficient. Sometimes marks were made on coins from an earlier period, often badly preserved to confirm their value or return them into circulation.
Countermarks have been identified on many different coins issued by some cities in the Roman province of Bithynia and Pontus. The countermarks include dates, value signs, busts of deities and emperors, as well as symbols of an unknown meaning. Some of the coins had countermarks of other cities, suggesting a wider circulation than the territory of their local center. During the presentation, individual types of countermarks, their possible chronology, and possible reasons for their placement on some coins of Bithynia and Pontus during the Roman period will be discussed.