Tremissis

Moneta Historical Research by Tom Schroer

"Tremissis" is a Latin word which was created by analogy to the term "semissis". Semissis ("semis" in its nominative form) was probably originally a contraction for "semi as" and came to denote a coin half the value of another. "Tremissis" probably came from "triens as", meaning a third of an as, and came to mean a coin having 1/3 the value of another. The term is usually applied the late Roman third of the golden solidus. The shortened form "tremis" is also sometimes used.

The solidus (Latin for "trustworthy") was the golden coin introduced by Constantine I at the end of 309 or beginning of 310. It replaced the "aureus", which had been of extremely variable weight in the third century. The solidus was not adopted by the Tetrarchy, and it was only after Constantine's final victory over Licinius I in 324 in the Second Civil War that the solidus (as well as Constantine!) reigned supreme.

Gold fractions of the solidus appeared at the Treveri mint simultaneously with the introduction of the solidus, but from their weight they appear to have been 3/8 of a solidus, or "1½ scripulum" (q.v.) pieces.  The first true half (semissis) did not make its appearance until 320 at Sirmium. The semissis continued to be struck until at least 867, but the 1½ scripulum piece was discontinued by about 385.  In its place Theodosius I substituted the tremissis. which was 1/3 of the solidus instead of 3/8.

The theoretical weight of the tremissis was 1/216 of the Roman pound, or about 1.51 grams, which corresponds very closely to its actual struck weight. Since the solidus, of which it was a fraction, was very stable in weight over the centuries, the tremissis varied little from its original 1.51 gram weight. In Roman times the tremissis, like all Roman gold, was usually in excess of 98% fine.

Gold fractions were never very common until about the fifth century, and at that time the tremissis became much more common than the semissis. The tremissis continued to be struck until well into Byzantine times (the last known are of the reign of Basil I (867-886)).