Roman Coin Denominations: Unity Details

As [AE] : This denomination, meaning ’unity’, was a standard unit in Roman coinages initially. It was first struck c.280 BC. From the beginning of the Empire it was struck in pure copper, making it look yellowish, but by the end of the 3rd century AD it was bronze. Hence, asses usually appear darker than dupondii or sestertii, and they are also smaller than the other two at a given time. The emperor is always shown wearing a laurel wreath on an as, which helps to identify it.

Dupondius [AE] : First issued during the Roman Republic, its initial value was two asses. Struck from a bronze alloy called orichalcum, it looks yellowish like the larger sestertius, however, starting with Nero, the emperor is always shown wearing a radiate crown which makes it easy to distinguish from sestertii and asses.

Sestertius [AE] : Introduced as a small silver coin in 211 BC, along with the denarius, its initial value was two and a half asses, or 1/4 of a denarius, but was changed to a very large bronze coin after 44 BC which was worth four asses. The coin shrunk in size slowly and disappeared in the 3rd century at which time it was made of bronze (and was rare).
This is a large coin, more than the US half dollar (30mm+) in size, and often shows great detail. During the Empire it was struck from a bronze alloy called orichalcum, making it look yellowish like the smaller dupondius, however, the emperor is always shown wearing a laurel wreath which helps to distinguish it, and it is much larger than an as.

Denarius [silver] : First issued c.211 BC, during the Second Punic War of Rome against Carthage (218-201 BC). The initial value of this coin was ten asses (from which its name is derived), the value was eventually changed to 16 asses. The coin was initially struck of very pure silver, almost 100%, but declined to 94% by Nero’s time, 90% by Hadrian’s, 73% by Commodus’ and finally to and below 50% by the reign of Severus Alexander. The amount of silver fluctuated up and down (as it was going down) due to attempted monetary reforms of several emperors. From about 238 AD (Gordian III) the silver content decreased sharply and the coin became very rare, disappearing totally around 296 AD, after over 500 years of use. Denarii are typically the size of a US dime.

Quinarius [silver] : The quinarius was a small silver coin of ancient Rome that was worth half a denarius. It was first minted in 211 BC, and then reintroduced in 101 BC with a different value of 8 asses. The coin often featured the head of Jupiter or Victory on the obverse, and a galley or a trophy on the reverse. One example of a quinarius is the one issued by Titus Cloelius in 98 BC, which had the head of Jupiter with a winged helmet on the obverse, and Victory crowning a trophy with a captive and a carnyx on the reverse . The quinarius was used mainly for circulation in Gaul, and was discontinued in the 3rd century AD.

Antoninianus [silver/bronze] : The name of this denomination, often abbreviated to ”Ant”, is derived from the name M. Aurelius Antoninus, commonly known to us as Caracalla, who introduced the denomination in 214 AD. The ancient name is not known.
The Antoniniani would stick around for the next 80 years. The value of this coin was two denarii when first issued, and while a silver coin, the silver content started out at only about 40% and declined rapidly over time. By the time of Gallienus, it turned into a bronze coin just a bit larger than the denarius, with little silver content. Hence, we can have AR Ant or AE Ant. Thanks to the monetary reforms of Aurelian, the coin returned to its original size, and was coated with a thin layer of silver called a ’wash’, which made it look silver again. However, most coins available to collectors will have this silver layer worn off, or barely visible, making the coin appear bronze. Ones with the layer intact sell at higher prices.
The silver content at its end was 5%, sometimes denoted on the reverse of the coin by the Roman numerals XXI, or XX, meaning 20:1, or 20 parts of bronze to one part silver. The Greek letters KA (=21) were also used for this purpose in some mints, mainly Serdicia. The coin disappeared during Diocletian’s reform of coinage in 294 AD, and for a short time after, small bronze coins with radiate heads of the emperors were issued known as ’post-reform radiates’ or ’bronze radiates’.
The silver Antoniniani are typically the size of a US quarter, but shrink to dime size for late-3rd century emperors and look bronze. They always show the emperor wearing a radiate crown. Furthermore, the emperors’ busts become more stylized over time, with a lower relief, making them look more similar.

Follis [bronze] : The follis, first issued by Diocletian in 294 AD, started out as a very large bronze coin with a silver wash, about the size of a US half dollar. The coin shrunk down to denarii size (15mm) over the next fifty years or so. There was also a coin issued under Severus II Caesar (306-307 AD) which is small compared to the other folles of the time, and called a quarter-follis. Follis is not the ancient name for this coin, however, since it is not certain what they were called (possibly ’nummus’ ?). Follis simply means
’bag’, since they were placed in bags for transport, or even circulated in large amounts
as a ’bag unit’.
Folles therefore start out as large bronze coins, and shrink down to a size smaller than a dime size by mid-4th century. The emperor is always shown wearing a laurel wreath, with a low relief stylized bust. Traces of silver may be seen on some. They were issued after the radiate head Antoniniani were discontinued, so no confusion is possible.

AE1, AE2, AE3, AE4 [bronze] : Finally, we get to a period around mid-4th century during which we don’t know the coin denominations (or there is a lot of disagreement).
Some collectors will use the term Centenionalis, Half-Centenionalis, or Majorina, however, to avoid confusion most collectors prefer to use the size scale shown in Table 4 below for these coins. The emperor is usually shown wearing a laurel crown on his head. Since the busts have a low profile and are very similar, it is rather difficult to tell Constantius II from Honorius for example if the legend is not clear enough. Some of the tiny late 4th century ones are sometimes less than desirable).
These scales should not be confused with a similar system used for Greek bronze coins and Roman provincial coins, where a coin may be classified as AE17 means that it is 17mm across. AE1 would be very tiny then! Also, since the coins are sometimes not round and may fall into different denomination depending on how they are measured, they may be classified as AE2/3 for example.

Table 4: AE Coin Sizes

It is difficult to distinguish between a follis and an AE coin denomination. Historically, Constantine I in 318 AD changed the relationship between the denominations, and the strandard was changing throughout this period. Bronze coins therefore no longer have a relation to precious metals like the denarius, Antoninianus or follis did. Therefore, coins from the time of Constantius II and Constans on will use the AE scale.