Rome was a colossus that straddled the world - an imposing superpower whose influence continues to the present day.
Ancient Rome began as a Republic ruled by a Senate and then became an empire dominated by a single ruler, the Emperor. The Roman civilization (combining both Republic and Empire) lasted for millennia. During the Empire, each new Emperor would place his own image on the coinage and, from time to time, monetary reforms would change the denominations and their relative values. Hence there is a great diversity of Roman coins to study and appreciate. At its height, the Roman Empire stretched from Britain to North Africa. Therefore, Roman coins may be found throughout the ancient world.
Among the coins produced by the ancient Romans the following denominations were some of the most important (and, thus, most likely to be encountered by the new collector):
Quadrans - After 90 BC, the Quadrans was the lowest denomination minted. It was worth one-quarter As (quadrans = "quarter." See below for description of the As). Unlike many Roman coins, Quadrans rarely featured a portrait of the Emperor. Instead, the bust of Hercules typically appeared on the obverse. Initially, the Quadrans was a bronze coin, but during the Empire it was produced in copper.
Assarius (also As) - In the Republic this was a bronze coin with the head of Janus on the front (obverse) and the prow of a ship on the back (reverse). During the Roman Empire the As was struck in pure copper. During the Empire it was the lowest valued coin in regular production.
Dupondius - The Dupondius was worth 2 Asses or half a Sestertius. It was a bronze coin during the Republic, but was made of brass during the Empire. During the reign of Nero a radiate crown was added to the portrait of the Emperor to help distinguish it from the As.
Sestertius - Most of these were minted as large brass coins during the time of the Roman Empire. Augustus set the value of the Sestertius as 1/100 Aureus (see below). A Sestertius was also worth four Asses.
Denarius - A small silver coin that became the most common coin minted for circulation. It was worth four Sestertii or sixteen Asses. Twenty-five Denarii were equivalent to one Aureus. According to the Bible, a Denarius was worth a day's wages for a typical workman (at least in the provinces).
Aureus - A gold coin valued at 25 Denarii and 100 Sestertii. Constantine I replaced the Aureus with the Solidus during the late Roman Empire.