Near the middle of the third century AD, Roman authorities began to realize that it would be desirable to have a method of tracking the mint that particular coins originated from. They devised a system of mint marks, a series of letters and symbols, placed in the exergual space on the reverse of a coin, that would allow them to determine which mints were issuing coins that failed to meet weight or precious metal content standards.

These mint marks did not see universal use throughout the empire until after the monetary reforms of Diocletian, but following the reforms, unmarked coins were to become the exception, rather than the rule.

Learning to read the mint marks is actually a fairly simple thing, so lets get started!

A basic mint mark is composed of three things:
1. A letter or letters for (P) Pecunia, (SM) Sacra Moneta, or simply (M) Moneta.
2. Letters indicating the particular mint. For example: NIK for Nicomedia, SIS for Siscia, etc.
3. A letter indicating the officina, or specific workshop of the mint. Officina in the Western empire used Latin letters: P, S, T, and Q for Prima, Secunda, Tertia, and Quarta. The Eastern mints used Greek letters: A, B, G, D.

As an example, look at the following mint mark:

We read this as: Sacra Moneta, Antioch mint, third workshop.

Of course, not all mint marks follow these rules exactly. Some coins have the workshop number located in the fields. Some place the officina mark before the mint name. Also, a number of mints had a greater number of different workshops , as many as 15 in some cases. Some even omitted the officina mark.

In any case, just learning the abbreviations used by the various mints will allow you to determine which mint produced a particular coin.

The chart below lists some of the later Roman mints and their mint marks.