How to Identify the Byzantine Follis

What It Is

The follis was introduced as part of Emperor Anastasius I's major currency reform of 498 AD, which for the first time gave Byzantine bronze coinage large, clearly marked denomination values instead of the small, poorly regulated bronze pieces used previously. It became the standard coin of everyday commerce for ordinary Byzantine subjects for centuries.

Obverse Design

The obverse shows a bust or, on many earlier issues, a full facing or profile portrait of the emperor, wearing imperial regalia, with an abbreviated Latin or (later) Greek legend identifying the ruler. Portrait style shifts noticeably over the centuries, from more naturalistic Late Roman-influenced busts to the flatter, more stylized and symbolic imperial images typical of the middle Byzantine period.

Reverse Design

The defining reverse feature is a large Greek numeral denoting the coin's value in nummi (the smallest bronze unit): a bold "M" for 40 nummi (the follis proper), "K" for 20 nummi (half-follis), "I" for 10 nummi (decanummium), and "E" for 5 nummi (pentanummium). Below the denomination mark, an officina letter (workshop identifier) and mint abbreviation typically appear in the exergue, and a cross or star often sits above the letter.

Size, Weight, and Metal

Struck in bronze (sometimes described as copper alloy), the follis was originally a large, heavy coin weighing around 9 grams at introduction, with a diameter that could exceed 30mm in the early 6th century; weight was gradually reduced across subsequent reigns due to periodic recoinage and economic pressure, so a "follis" from a later century may be noticeably smaller and lighter than one from Anastasius's original reform. Edges are plain and hand-struck.

Mint Marks

Below the large denomination letter, in the exergue, look for an abbreviated mint city name (such as CON for Constantinople, NIKO for Nicomedia, or ANTIOCH for Antioch) along with a Greek or Latin officina letter indicating which workshop within that mint struck the piece—useful for narrowing down both origin and approximate date within a reign.

Telling It Apart From Similar Coins

The follis is easiest to identify at a glance by its large size and the bold "M" mark, distinguishing it immediately from the smaller half-follis ("K"), decanummium ("I"), and pentanummium ("E") that make up the rest of the same Anastasian-reform denomination system. Comparing overall diameter and weight against known standards for a specific reign also helps separate an early, heavy follis from a later, reduced-weight example bearing the same basic design scheme.

Judging Condition at a Glance

Because bronze coins corrode and wear more readily than gold or silver, judge condition by how much of the emperor's portrait detail and the denomination letter remain visible, along with the completeness of the mint and officina marks in the exergue, which are often the first details to wear away or corrode on a heavily circulated piece.

Authenticity Red Flags

Look for a denomination letter and expected weight/size that do not match (for example, an "M" mark on a coin far too small or light to be a genuine full follis of its claimed reign), an implausible mint-and-officina combination, or a surface treated to look artificially aged. Genuine ancient bronze typically shows a natural, uneven patina built up over many centuries rather than a uniform chemical coating.