The Monetary Reform of Constantine
The monetary system of the Roman Empire underwent a considerable number of changes during the reign of Constantine. While he was still only a junior partner holding the rank of Caesar, Constantine reduced the weight of the follis at the mints then under his control (London, Lugdunum, and Treveri) and again reduced it soon after his elevation to the rank of Augustus (March, 307 AD). The final reduction to c. 68 grains was made some months later.
This was only keeping in line with the reductions of the follis being made by the other rulers of the Empire, but about 310 AD Constantine made some important changes on his own initiative. In place of the aureus 5.45 grams (60 to the lb. of gold 327 grams) he introduced a new coin called the solidus, which was struck at 72 to the lb or 4.54 grams. Other gold denominations introduced were the semis (½ solidus 2.27 grams) and the 1 ½ scripulum (3/8ths solidus 1.70 grams). The aureus continues to be struck in the East until the defeat of Licinius in 324 AD when the solidus became the standard gold coin of the entire Roman Empire. The aureus, however, was still occasionally struck up to about the end of the 4th century.
Later in the reign, a silver piece tariffed at 24 to the solidus was also struck, but although it was given the name siliqua, it appears to be of the same weight as Diocletian’s argenteus (96 to the lb. of silver). In addition to the siliqua, a larger silver piece of struck at 72 to the lb. was introduced. The name of this denomination was the miliarense and, as can be seen from the weights, the siliqua was equivalent to ¾ of the miliarense which was, in turn, equivalent to 1/18 of the solidus. As such, Constantine changed the silver/gold ratio to 18:1, which was an appreciation of gold rising from the Diocletian standard when the ratio stood at 15.6:1. We thus have the following system in the precious metals:
1 AU solidus = 2 semisses = 18 AR miliarensia = 24 AR siliquae.
As in the case of the 1 ½ scripulum, there is also a silver denomination that appears to stand in no convenient relationship to the other denominations. This piece is slightly heavier than the miliarense (1/60 lb.) and is usually referred to as a heavy miliarense.
Soon after the defeat of Maximinus II in 313 AD, Constantine and Licinius reduced the follis to c. 18-20 mm in diameter and 48 grains in weight. Thereafter the denomination is usually referred to as an AE 3. This module just survived the introduction of the GLORIA EXERCITVS type in 330 AD, but was then reduced to 17 mm and 30 grains. A few years later, possibly in 336 AD, there was a further reduction in weight to 20-25 grains. These bronze coins of the last 7 years of Constantine’s reign occasionally decline to AE 4 module (under 17 mm.) especially after the weight reduction in 336 AD.
The inflationary pressures continued to rage during this period so much so that the changes in the bronze coinage of the late Roman Empire reflect a near-constant decline in weight and size as to blur the distinction between denominations. Therefore, bronze coinage is divided into four general groups denoted as AE1, AE2, AE3, and AE4 based upon diameter as follows:
Classification by Diameter
AE1 from 25 millimetres
AE2 from 21 millimetres
AE3 = from 17 millimetres
AE4 under 17 millimetres
In the final years of Constantine’s reign, there was a marked increase in the output of silver coinage, from a network of eight mints throughout the eastern and western provinces of the empire. Issues in the name of the Caesar Delmatius are, however, of considerable rarity. The upward-looking gaze of the imperial portrait is a feature that first appeared on the Constantinian coinage in 325 AD. It is certainly suggestive of divine awareness, and may well be a direct allusion to Christianity itself, for this was the year in which the celebrated Nicaean Council was summoned, resulting in the formulation of the Nicene Creed.