Instructions
Turn the coin so the reverse side -- the side without the emperor's portrait -- is facing up. Look below the reverse design. This area of the coin is called the "exergue" and contains the mint information.
Look for the string of one to seven letters appearing in the exergue. These letters identify the city in which the coin was minted. For example, Rome is represented by R or RM and Alexandria is represented by ALE.
Look to see if there are any letters or numbers appearing after the city abbreviation -- this identifies the mint workshop where the coin was created. Eastern Roman empire coins used Greek letters to indicate workshop numbers. For example, the Greek letter alpha or "A" means first workshop; beta means second workshop and so on. Coins from the western empire used Latin to identify workshops: prima meaning first workshop, secunda meaning second workshop and so on.