Understanding Late Roman Bronze Coin Denominations

When you sort through a lot of uncleaned late Roman bronze coins, one of the first things you notice is the variation in size. Some pieces are as large as a 10p coin; others are barely bigger than a shirt button. These differences reflect a monetary system that underwent dramatic inflation and repeated reform between the late 3rd and early 5th centuries. Understanding the denomination system will help you identify and appreciate what you have found.

Why We Use the AE Classification

The abbreviation "AE" comes from the Latin aes, meaning bronze or copper. Nineteenth-century numismatists invented this classification because we do not know with certainty what the Romans actually called many of their late bronze denominations. Weight standards changed so frequently between Diocletian (284 AD) and Anastasius I (498 AD) that scholars have never definitively assigned original names to every issue. A few ancient literary references mention terms like centenionalis and maiorina, but scholars disagree about which specific coins those names apply to.

Rather than force uncertain ancient names onto coins, the AE system uses an objective, measurable criterion — diameter — to classify coins into four groups:

AE1 — Over 25 mm diameter, typically 8–15 grams. These are the large, impressive pieces: the original Diocletianic follis and its immediate successors. Uncommon in most uncleaned lots.

AE2 — 21–25 mm, typically 4–6 grams. Medium-sized coins, including the maiorina of the 348 AD reform. Less common but present in many lots.

AE3 — 17–21 mm, typically 2–3.5 grams. The workhorse denomination of the late empire. This is what you will find most frequently in uncleaned lots.

AE4 — Under 17 mm, under 2 grams. The smallest pieces, often with minimal detail. Very common from the late 4th century onward.

To classify your coins, measure the diameter at the widest point with a digital caliper. A digital scale accurate to 0.01 grams will confirm your classification.

The Follis: Diocletian's Reform (294 AD)

In 294 AD, the emperor Diocletian overhauled the Roman monetary system with a comprehensive reform introducing a trimetallic system of gold, silver, and bronze coins. The flagship bronze denomination — now usually called the nummus or follis — was a substantial coin: 27–30 mm in diameter, 9–12.5 grams in weight, with a thin silver wash over a copper core containing approximately 4–5% silver.

The word follis literally means "bag" in Latin, and likely referred to a sealed bag containing a specific number of coins rather than to the individual coin itself. The term nummus (simply meaning "coin") is now considered by many scholars to be the more accurate ancient name. Despite this, dealers and collectors still widely use "follis," and you will see it frequently in catalogues and online listings.

The Great Decline: 307–348 AD

What happened next is one of the most dramatic inflationary declines in numismatic history. Over roughly fifty years, the follis shrank by approximately 90% in weight and 50% in diameter. The silver content dropped from around 4–5% to effectively nothing.

Under Constantine I (306–337 AD), the bronze coinage shrank steadily. By the 330s, the standard bronze was an AE3/AE4 of about 15–17 mm and under 2 grams — a mere fraction of Diocletian's original. The most common types from this period are the GLORIA EXERCITVS ("Glory of the Army") reverses showing two soldiers flanking military standards, struck in enormous quantities and found frequently in uncleaned lots.

The Reform of 348 AD

By 348 AD, the bronze coinage had deteriorated to near-worthlessness. The emperors Constans and Constantius II launched a major reform introducing new, larger denominations under the reverse legend FEL TEMP REPARATIO ("Restoration of Happy Times"), commemorating the 1,100th anniversary of Rome. This produced three main denominations:

• The heavy maiorina (AE1/AE2), about 5–7.5 grams and 20–24 mm, with a small silver content. It featured the famous "Galley" reverse showing the emperor on a ship steered by Victory.
• The light maiorina (AE2), about 4–5 grams, with the "Falling Horseman" reverse: a soldier spearing a fallen enemy horseman.
• The centenionalis (AE3), about 2–3 grams and 17–21 mm. The Falling Horseman type also appeared at this smaller size.

The Falling Horseman is one of the most common types in uncleaned lots. These coins were produced in enormous quantities for Constantius II, Constantius Gallus, and Julian as Caesar, and survive in huge numbers today.

The Valentinian Period: 364–378 AD

Under Valentinian I (364–375) and Valens (364–378), the AE3 of about 17–19 mm and 2–3 grams was the dominant denomination. Common reverse types include GLORIA ROMANORVM (emperor dragging a captive) and SECVRITAS REIPVBLICAE (Victory advancing left with wreath and palm). These are extremely common in uncleaned lots from Balkan and Eastern Mediterranean sources.

The End of the Line: Theodosius and After

Under Theodosius I (379–395) and his successors, the bronze continued to shrink. By about 400 AD, the AE4 — tiny coins under 17 mm and often under 1.5 grams — completely dominated bronze production. These diminutive pieces, sometimes called nummi minimi, are often the most challenging to identify due to their small size and worn surfaces.

What You Will Most Likely Find

Most uncleaned lots sourced from the Balkans, Turkey, or the Holy Land are dominated by AE3 and AE4 coins from three main periods:

• Constantinian AE3/AE4 (330s–340s) — GLORIA EXERCITVS types, approximately 15–18 mm, 1.5–2.5 grams
• FEL TEMP REPARATIO "Falling Horseman" (348–355) — AE3 to AE4, approximately 14–20 mm, 2–4 grams
• Valentinian/Valens AE3 (364–378) — GLORIA ROMANORVM and SECVRITAS types, approximately 17–19 mm, 2–3 grams

Further Reading

• Doug Smith's Size Scales for Ancient Coins — forumancientcoins.com
• FLAME Project: Classifying Roman Bronze Coins c.325–491 CE — Princeton University
• Tesorillo: Identifying Late Roman Bronze Coins — tesorillo.com
• Doug Smith's 12 Common Uncleaned Coins — forumancientcoins.com