Ancient Roman coins serve as more than historical curiosities; they tell a significant history of the Roman and Western culture. The varieties of their metal, the method by which they were produced, and the imagery they bear unveil important aspects of the Roman culture and the various Western societies that were formed through Rome's cultural dissemination.
Prior to having minted coins, Roman trade operated by a system of livestock bartering. As the Roman Empire transitioned from livestock bartering into local currencies and eventually an imperial currency, the language reflected the livestock roots of Roman trade. The Latin word "pecunia," used by Romans to signify money, derives from the Latin "pecus," meaning "livestock." Though having initially adopted Greek currency in local markets, the Romans established their own currency in the third century A.D.
Though the base coin of the empire was the "as," the standard denomination of the Roman trade currency was the "denarius," initially valued at 10 asses but devaluing later to 16 as silver became more common in the empire. The value of other coins--such as the "sesterius," worth one-quarter of a denarius, or the aureus, worth 25 denarii (the plural of denarius)--were always determined by the value of the denarius itself.
Three primary metals were used in the minting of ancient Roman coins. In early days, various copper alloys, including bronze, were used; being both easy to forge and readily found, copper coins nonetheless failed to find establishment at the heart of the Roman trade. In the third century A.D., however, silver became more readily available and was found to be of greater value--not only because of its rareness, but its aesthetic value--and became the standard by which other metals were judged. Gold, though always appreciated for its beauty and rareness, was too rare to ever become a standard and instead remained a status of symbol and luxury.
Most ancient Roman coins were produced, as in other cultures, by placing a blank coin-shaped piece of metal between two hardened dies that bore images and hammering the upper die atop the coin. This method, in which the dies could be reused thousands of times, enabled quick, efficient and uniform production of a usable currency for the empire.
As with modern coins, those of the Ancient Romans most commonly bore images of heroic political and military figures, as well as poignant sayings and mottoes. In early days, the coins still borrowed from Greek mythology--some coins have been found that bear the image of Hercules, which was the centrepiece of Alexander the Great's currency. However, the reverse side of the same type of coin bears an image of a she-wolf suckling the two founders of Rome, Remus and Romulus. Later coins principally bore the images of the emperors at the time of their minting.