The Roman Empire encompassed modern-day Europe, north Africa and parts of the Middle East, stretching from Spain to Palestine during its heyday. Romans began minting coins at the beginning of the third century B.C. Roman coins typically have a profile of an emperor on the front -- or obverse -- of the coin, and a picture and mint mark -- the mark identifying where the coin was created -- on the reverse. Mint marks consist of a one- to seven-letter abbreviation of the city's name in which the coin was minted. Mint marks can be deciphered if you know what to look for.
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.
The mint mark may also include the letters "SM" before the city abbreviation, which stands for "Sacra Moneta," meaning "sacred money." Use a map of the Roman empire to help you match city abbreviations to the mint mark. If you get stuck, use the workshop number as a clue if you should be looking in the eastern or western Roman empire for your city.