This product is a Roman Imperial bronze coin from the era of Constantine I, dating back to the 4th century AD. It commemorates the 20th anniversary of Constantine's vows in Thessalonica, as indicated by the XX marking on the coin. The denomination of the coin is Follis, and it is an uncertified piece of ancient history that holds significance in Roman numismatics. This coin would be a valuable addition to any collection of ancient Roman coins, offering a glimpse into the historical period of Imperial Rome.