One of the things that makes collecting ancient coins so much fun is the challenge of attributing them. Although one might well argue the point, the word "Attribute" (With emphasis on the second syllable) can be loosely defined as identifying a coin or artifact with respect to certain criteria. Usually, attribution involves more than simply identifying a coin. Acollector could say, "This is a denarius of the Roman emperor Antoninus Pius." The collector may have correctly identified the coin this does not constitute a complete attribution. Usually the minimum acceptable attribution contains the ruler's name and the reverse type. If the collector finds a coin in a dealer's junk box and, by means of the portrait style and parts of the inscription identifies it as a denarius of Antoninus Pius, this is one step in the attribution of the coin. If he or she goes on to make a statement that it is a FELICITAS AVG type based on a partial legend and the items held in the hands of the female figure, then that collector can claim to have attributed the coin. Often, dealers do little more than this and print or write the information on an insert card to put in a flip behind the coin. A full attribution can involve much more though, and this is what makes the hobby so interesting for some of us. There is an enormous corpus of knowledge out there dealing with ancient coins, and this is especially true of Roman coins. The Romans themselves collected and tried to attribute the beautiful Greek coins struck by the independent rulers and city - states a few hundred years prior to their own time. Today, we have access to the material so painstakingly assembled by scholars of the past. The serious ancient coin collector and professional numismatist specializing in Roman coins might have the following books in his or her library:
Roman Coins and their Values By David Sear.
The ten volumes of the Roman Imperial Coinage by Mattingly et al.
The five volumes of the Roman Silver Coins by Seaby.