Among the many collections of ancient coins that can be assembled, one of the most challenging and desirable is that of the "Twelve Caesars." They can be collected in copper (and its principal alloys), silver or gold; the latter is the most difficult to complete. Thus, it is a rare opportunity indeed to present this set of "Twelve Caesars" gold aurei.

The popularity of these rulers as a group derives from one of the great literary works of antiquity — Suetonius' De vita Caesarum, today commonly known as The Twelve Caesars. It was composed in the early second century A.D. by Gaius Suetonius Tranquillus, who focused on 12 rulers of Rome, a group comprised of the dictator Julius Caesar and the first 11 emperors.

These men ruled in a volatile and formative period of Roman history, overseeing the collapse of the Republic, civil war, and the rise of an empire that would dominate the Mediterranean world.

Julius Caesar needs no introduction to those familiar with the foundations of Western Civilization, nor does his successor, Augustus, who actually established the empire. Tiberius is also a household name — principally, perhaps, for having reigned during the ministry of Christ. Caligula, Claudius and Nero are all popular emperors known for their eccentricities. Together, these six men comprise the rulers of Julio-Claudian Dynasty.

That dynasty fell in the summer of A.D. 68, when civil war erupted after nearly a century of domestic stability. The war raged for nearly two years, and four men — Galba, Otho, Vitellius and Vespasian — were hailed emperor by the senate in the year 69. Though less familiar than the Julio-Claudians, the lives of these civil war emperors are no less remarkable.

The last men to rule in the period of the "Twelve Caesars" were the three emperors who formed the Flavian Dynasty. It was founded by the aforementioned Vespasian, who came to power at the end of the civil war, and was maintained by his two sons, Titus and Domitian. After the murder of Domitian in a palace coup, the period of the "Twelve Caesars" came to an end and a new era of Roman history began, commonly known as that of the adoptive emperors.

All 12 coins shown here are of a denomination called an aureus, a coin of nearly pure gold that was the economic standard of the Roman world for about four centuries. Each of the aurei bears a portrait of the issuer on the obverse and a design of some importance on the reverse.

Two aurei have as reverse types the portraits of deceased family members, and thus require comment. The aureus of Augustus (at the time known as Octavian) depicts Julius Caesar, the great-uncle from whom he inherited a fortune in gold and the political legacy that was the basis of his own rise to supreme power. The aureus of Caligula depicts his deceased mother Agrippina (a granddaughter of Augustus), who was an important source of his legitimacy as emperor.

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