Miliarense

About the time of the conclusion of the Second Civil War with Licinius I, Constantine I began striking the miliarense (plural: miliarensia), a new silver denomination of about 4.3 grams, in addition to the argenteus (or siliqua) of about 3.1 grams. The name "miliarense" itself literally means "containing one thousand units" (from "miliarius") and is not attested to in ancient sources until after 348. The possible origin of the name lies in the fact that a heavy  miliarense was "roughly" equal to a thousandth of a pound of gold (a heavy miliarense was worth 1.6 siliquae, so  .625 heavy miliarensia/siliqua x 24 siliquae/solidus x 72 solidi/pound of gold = 1080 heavy miliarensia/pound of gold). Using the average "as-struck" weights of the heavy miliarense (5.2 grams) and the early siliqua (3.15 grams) gives an even closer figure of 1047/pound.

The miliarense was probably based on a theoretical standard of 72 to the Roman libra (pound), giving it the same theoretical weight as a solidus (q.v.), about 4.55 grams. However the Roman government always over-valued its silver by 5-10% and thus the actual weight of 4.3 grams is about what is to be expected.  Its relationship to the early siliqua (struck at 96 to the libra) is therefore in the ratio of 96:72 (4 to 3), so it actually was equal to about 4/3 siliquae.

About 355 the siliqua was dramatically reduced by Constantius II to about 2.0 grams (probably a theoretical 144 to the libra, or 2.26 grams), so the value of the miliarense relative to the siliqua increased to approximately 2:1. By the late fourth century the miliarense had decreased in weight to about 4.0 grams, but its relationship to the siliqua was steady, since siliquae were then generally struck at between 1.9 and 2.0 grams.

The miliarense continued to be struck through the sixth century although its weight was reduced further about the middle of that century. As with all late Roman silver, the fineness was between 93 and 97% for the life of the denomination.

Some of Constantine's new silver coins seem to have been struck at a different standard of about 60 to the libra, although they are very scarce.  However the heavier coins continued to be struck in subsequent reigns alongside the lighter silver and hence have acquired the name of "heavy miliarense". Their theoretical weight is 5.46 grams, but with the normal over-valuation they were only struck at about 5.16 - 5.20 grams.

Since there are actually two different coins which use the name miliarense, convention has been to either use the name "miliarense" or "light miliarense" for those struck at about 4.2 - 4.3 grams, and the term "heavy miliarense" for those struck at about 5.1 - 5.2 grams.

Also see Heavy miliarense