The Roman economy was a massive, living machine, and its coins were the gears that kept it turning. If you were to dump a merchant’s leather satchel onto a table in the second century, you wouldn’t just see silver; you would see a calculated hierarchy of metals—gold, silver, brass, and copper—each with a specific “rank” in the imperial accounting books.
In our Numiscurio gallery, we often talk about the history behind the portraits, but understanding denominations is where the real technical detective work begins. It is the study of “unit details”—the mathematical relationship between a soldier’s annual salary and the price of a single loaf of bread. From the prestigious gold Aureus to the humble copper As, the Roman monetary system was a shifting landscape of value that mirrored the rise and fall of the Empire itself.
The Silver Standard: The Denarius
The Denarius is perhaps the most iconic “unity” in the history of money. First struck around 211 BC during the desperate years of the Second Punic War against Carthage, it was born out of a need for a stable, high-quality currency to fund Rome’s struggle for survival. Its name literally reflects its original value: denarius means “containing ten,” as it was initially worth ten copper asses (a value that later shifted to sixteen).
For over five centuries, the Denarius was the standard by which all other wealth was measured. However, its story is also one of a long, slow “fading.” In the early days of the Republic, these coins were struck in nearly 100% pure silver. By the time of Nero, that purity had dipped to 94%; under Hadrian, it was 90%. As the Empire faced greater internal and external pressures, the silver content plummeted—dropping to 73% under Commodus and eventually crashing to 50% or less by the reign of Severus Alexander.
As a collector, I find the “physics” of the Denarius fascinating. They are typically small—roughly the size of a modern US dime—yet they carried the weight of the Roman economy on their shoulders. While various emperors attempted monetary reforms to stabilize the “unity” of the coin, the silver content continued a volatile downward trend. After the reign of Gordian III in 238 AD, the silver vanished so rapidly that the Denarius became a rarity, finally disappearing entirely around 296 AD.
Holding a Denarius today is like holding a timeline of Roman history. The crisp, high-purity silver of the early Empire eventually gives way to the duller, debased specimens of the late 3rd century, marking the exact moment when the economic strength of Rome began to transform.
The Quinarius: The Silver Half-Unit
The Quinarius served as the small-scale silver companion to the denarius, carrying exactly half its value. First introduced in 211 BC during the height of the Second Punic War, it saw a significant reintroduction in 101 BC, at which point it was valued at 8 asses.
In our collection, these coins are distinctive for their dynamic military and religious imagery. They frequently featured the head of Jupiter or Victory on the obverse, while the reverse often depicted naval galleys or battle trophies. A classic specimen of the “technical detail” found on these coins is the 98 BC issue by Titus Cloelius: it showcases Jupiter in a winged helmet, with the reverse capturing the dramatic scene of Victory crowning a trophy alongside a captive and a Celtic carnyx (war trumpet).
Because of its specific weight and value, the Quinarius found its primary use in the border regions and was heavily circulated in Gaul. Much like the denarius, it eventually faded from the Roman monetary landscape, being officially discontinued during the economic shifts of the 3rd century AD.
The Bronze Foundation: Sestertius, Dupondius, and As
While silver handled the “middle-class” transactions, the base metal denominations were the true currency of the Roman streets.
The Sestertius:
The Sestertius has one of the most fascinating “evolutions” in Roman numismatics. When it first appeared alongside the denarius in 211 BC, it was actually a tiny silver coin valued at two-and-a-half asses (1/4 of a denarius). However, following the reforms after 44 BC, it was transformed into the massive, iconic bronze coin we recognize today—reset to a value of four asses.
In our gallery, the Sestertius is always a showstopper. It is a substantial coin, typically larger than a US half-dollar (30mm+), providing a wide “canvas” for some of the most intricate artistic details found in the ancient world. During the height of the Empire, it was struck from orichalcum, the golden-toned brass alloy that gives it a yellowish glow similar to the smaller dupondius.
For a collector, the Sestertius is easy to spot: it is significantly larger and heavier than a standard as. To distinguish it from the yellowish dupondius, simply look at the portrait—the emperor is always shown wearing a laurel wreath rather than a spiked radiate crown. While this “giant” of the Roman purse slowly shrunk in size and grew rare during the economic crises of the 3rd century, the early high-quality specimens remain the ultimate prize for any “Modern Curator.”
The Dupondius:
Originally introduced during the Roman Republic, the Dupondius was valued at exactly two asses. This denomination was struck from orichalcum—a distinctive brass alloy that gives the coin a bright, yellowish hue, very similar to the much larger sestertius.
Because the color and size could sometimes be confusing in a crowded market, a brilliant design change was made starting with the reign of Nero: the emperor began to be depicted wearing a radiate crown (a crown of sun-like spikes). This specific artistic choice serves as a permanent “technical marker,” making it incredibly easy for us today to distinguish the dupondius from the sestertius or the as, which traditionally feature the laurel wreath.
The As:
The basic copper unit. This was the “small data” of the Roman market—the coin used for wine, oil, and everyday necessities. Four Asses made one Sestertius.In the Roman monetary system, the As was the essential “unity”—the basic building block of everyday trade. First struck around 280 BC during the Republic, it survived for centuries as the empire’s primary small-change denomination.While its value remained a constant point of reference, its appearance shifted through the ages. During the early Empire, the As was minted in pure copper, which originally gave it a bright, reddish-yellow glow. However, by the late 3rd century AD, the transition to bronze became standard. Because of this metal composition, you’ll notice that Asses in our collection usually appear much darker than the brassy Sestertii or Dupondii. They are also consistently smaller and thinner than their higher-value cousins from the same time period.
The Golden Peak: The Aureus
At the absolute top of the pyramid sat the Aureus. Struck in near-pure gold, the Aureus was a concentrated store of wealth, generally valued at 25 silver Denarii. These were rarely seen by the common farmer; they were used for massive military donatives, high-stakes commerce, and the private hoards of the senatorial elite. Even in the humidity of our Costa Rican climate, the gold Aureus remains a perfect specimen, untouched by the oxidation that affects its bronze cousins.
The Evolution of Unity
The system wasn’t static. In the 3rd century, a new “unity” was introduced to combat inflation: the Antoninianus (or Double Denarius). Much like the Dupondius, the emperor is shown with a radiate crown, but the coin was intended to be silver.
Eventually, the weight and purity of these coins plummeted, leading to a total transformation of the system under Diocletian and Constantine, who introduced the Follis and the legendary gold Solidus.
The Antoninianus: The “Double Denarius” Hack
The Antoninianus (often abbreviated as “Ant”) is perhaps the most famous “technical hack” in Roman monetary history. Introduced in 214 AD by Marcus Aurelius Antoninus—better known as Caracalla—its ancient name remains a mystery. It was designed to solve a massive liquidity crisis: legally, it was worth two denarii, yet it only contained about 1.5 times the silver.
This coin defines the 3rd-century economic collapse. While it began with a 40% silver standard, the purity plummeted rapidly.
The Gallienic Crash: By the reign of Gallienus, the “silver” coin had essentially become a bronze unit, barely larger than a dime and containing almost no precious metal.
The Aurelian Reform: Emperor Aurelian attempted to restore the coin’s dignity by returning it to its original size (roughly the size of a US quarter) and applying a thin silver “wash.”
You’ll notice that most specimens today appear bronze because this thin silver layer has worn away. Coins with the original silvering intact are highly sought after and command a premium.
Toward the end of its life, the Antoninianus carried a specific “data mark” on the reverse: the Roman numerals XXI (or XX) or the Greek letters KA. These were not dates; they were a metallurgical guarantee meaning 20:1—twenty parts bronze to one part silver (5%).
The Follis: The “Bag” Unit
First issued by Diocletian in 294 AD, the Follis began its life as an impressive, large bronze coin roughly the size of a US half-dollar. Though its ancient name remains a mystery (some scholars suggest nummus), the word “Follis” actually means “bag”—a reference to the large leather pouches used to transport these coins in bulk.
The evolution of the Follis is a story of “shrinking data”:
Initial Scale: At its introduction, it was 30mm+ and coated in a thin silver wash.
The Quarter-Follis: By the time of Severus II (306–307 AD), we see smaller experimental units.
The Great Shrink: Over the following 50 years, the coin steadily diminished in size, eventually becoming smaller than a dime (approx. 15mm).
Identification Tip: The emperor is almost always shown with a laurel wreath and a highly stylized, low-relief bust. Unlike the earlier Antoninianus, there is no radiate crown, so the two are easily distinguished.
The AE Scale: A Classification help
By the mid-4th century, the relationship between bronze coins and precious metals had effectively collapsed. Because historians and collectors often disagree on the ancient names for these coins (terms like Centenionalis or Majorina are frequently debated), the numismatic community relies on a technical size-based scale known as the AE system.
| Denomination | Size Range | Modern Comparison |
| AE1 | Over 25 mm | Large/Impressive |
| AE2 | 21 – 25 mm | Quarter-sized |
| AE3 | 17 – 21 mm | Nickel-sized |
| AE4 | Under 17 mm | Smaller than a dime |
.. and quinarius? 😉
you are right !!! Seems that one got lost on the way.