Evolution of the Nummus: Base Copper Unit of Byzantium

Illustrated Specimen Details: Byzantine 40 Nummi

Example Specimen: 40 Nummi (Follis), 813-820 (Byzantine Empire)

Authority & Design: This copper follis represents a value of 40 nummi and was struck under the authority of Emperor Leo V the Armenian (813-820), a prominent general of Armenian origin who ascended the throne after a successful rebellion against Michael I Rangabe. Shortly after his coronation, Leo V appointed his son Symbatios as co-emperor under the royal name of Constantine. The obverse features the crowned facing busts of the co-rulers depicted in classical Byzantine style: the bearded Leo V on the left and the beardless Constantine on the right. Both wear the traditional chlamys (a state cloak worn by emperors and high officials) and are depicted without holding the akakia. The reverse features a large central letter M, which serves as the traditional Greek numeral designation for the denomination of 40 nummi. It is accompanied by a Christian cross at the top, while the flanking indicators XXX and NNN along with the officina letter A designate the Constantinople mint marks and dating elements.

Numismatic Note: While this specific issue is a cornerstone of Byzantine copper collections, it frequently encounters attribution discrepancies in various reference catalogs. Due to similarities in stylistic execution and legends (LEON S CONST), it is occasionally misattributed to Leo III the Isaurian with Constantine V (717-741). However, historical stylistic analysis firmly dates this distinct specimen to the joint reign of Leo V the Armenian and Constantine (813-820).

1. BYZANTINE EMPIRE (5th-9th centuries): 1 nummus = 1/5 pentanummium = 1/10 decanummium = 1/40 follis
2. ROMAN EMPIRE (3rd-5th centuries): nummus standard

NUMMUS as a coin name. The nummus (plural: nummi) was a fundamental copper or bronze coin utilized extensively throughout the late Roman Empire and the Byzantine Empire. The term is most commonly applied by numismatists to define the small, low-value Byzantine copper denominations issued between the 5th-9th centuries.

Historical Evolution and Metrology of the Nummus

The word nummus originates from the Latin term meaning simply "coin" or "money" in a broad sense. This was derived from the ancient Greek word nomos (or nomisma), which was historically used by the Greek colonies in Southern Italy to denote currency. In numismatic history, the role of the nummus transitioned from a generic term into a highly specific base unit of account.

From the Roman Republic to the Late Empire

During the Roman Republic and the early Empire, the term did not denote a single specific coin but could refer to almost any standard piece of money, such as the silver denarius, the gold aureus, or the bronze sestertius (which often acted as the primary unit of account).

As the Roman monetary system faced severe economic crises during the 3rd-4th centuries, the term gradually became attached to the smallest bronze issues. Following the comprehensive reforms of Diocletian and subsequent rulers, these small base-metal coins began to dominate daily local markets, often classified by modern collectors under the generic terms AE3 and AE4, or as the "centenionalis nummus".

The Byzantine Monetary Reforms

The nummus achieved its most distinct and official status as a precise denomination at the turn of the 5th-6th centuries during the comprehensive monetary reforms of Byzantine Emperor Anastasius I Dicorus. In this newly structured system, the individual copper nummus became the absolute base unit of currency.

Because a single nummus was exceptionally small (often weighing under 1 gram) and possessed very low purchasing power, the mints primarily struck larger, multi-nummi denominations. To ensure easy identification among a largely illiterate population, each coin featured a prominent Greek numeral indicating its exact value in nummi:

• M = 40 Nummi (The Follis)
• K = 20 Nummi (The Semifollis)
• I = 10 Nummi (The Decanummium)
• E = 5 Nummi (The Pentanummium)
• Δ, Γ, B, A = Regional fractions representing 4, 3, 2, and 1 nummus respectively

In addition to these mainstream imperial issues produced at the central mints, provincial mints such as Alexandria and Carthage struck localized variants with specialized numerical systems tailored to regional trade requirements.

The intrinsic value and manufacturing quality of the nummus remained relatively low. For an extended historical period, it required 7200 individual nummi to equal the value of a single high-purity gold solidus. Despite its low individual worth, this highly structured fractional system proved incredibly resilient, facilitating daily marketplace commerce across the Mediterranean world for centuries.