Byzantine coinage spans almost 1000 years from the reign of Anastasius I to the Ottoman conquest. There are many denominations and that they change over time. It 's hardly surprising that discussing the Byzantine denominations is complex. The early period is a bit
complex, because different mints struck coins to different standards. The last (Palaeologan) period also has its difficulties, because no one
is really sure about the relationship between the different denominations.
At the start of the Byzantine period – usually taken to be the currency reform inaugurated by Anastasius I in 498 CE – the basic gold coin is the solidus (Latin) = nomisma (Greek) which had existed since the time of Constantine I. The solidus had a nominal weight of 4.5g (= 4 scripula = 24 carats = 1/72 of a Roman pound) In fact, the weight and fineness remain surprisingly stable from the 6th century until debasement sets in in the 11th century, though in the sixth and seventh centuries some light-weight solidi of 20, 22 or 23 carats were issued, normally with a different signature in exergue to distinguish them from full-weight coins. Because of the stability of the solidus, it became widely used internationally; in medieval English this coin became known as the bezant.
Fractions of the solidus were also struck: the semissis = ½ solidus and the tremissis = 1/3 solidus. We also (but rarely) encounter multiples of the solidus, though these are always commemorative ceremonial issues, closer to medallions than coins for general circulation.
Early Byzantine silver coins are rare in the East and were also used mainly for ceremonial issues. The largest denomination is called the miliarense, but there are two weight standards, heavy (5.4g = 1/60 pound)) and light (4.5g = 1/72 pound). The siliqua = ½ miliarense. In sixth century Italy and North Africa, there was more extensive use of silver with some denominations based on those previously issued by the Vandals and Ostrogoths, which were multiples of the copper coinage. So in Italy, for example, you find silver 250-nummi and 125-nummi pieces as well as the siliqua and fractions thereof.
Anastasius I completely reformed the copper coinage in 498. The tiny, badly struck nummus coins which characterized the earlier 5th century were replaced by large and clearly marked multiples of the nummus. Greek, as indicated in the table below, uses letters to represent numbers, A = 1, B = 2, Γ = 3, Δ = 4, E (ε) = 5, ζ (S) = 6, … I = 10, K = 20, Λ = 30, M =40, etc. The largest denomination was the follis = 40 nummi and it was marked with an M. The original weight standard of the follis (it changed over time) was 18 to the pound, and since a solidus was theoretically worth 20 pounds of copper, you can work out that 1 solidus = 360 folles.
The smaller denominations are fractional folles, normally the half-follis (K), the decanummium (I) and the pentanummium (ε). In the West, the same denominations were issued, but marked with Roman numerals instead of Greek letters: follis (XXXX), half-follis (XX), decanummium (X) and pentanummium (V). And under the emperor Phocas, even the Eastern mints generally used Roman numerals as denominational marks. During his reign a three-quarter follis (XXX) was also struck.
But, just to complicate matters, there were a couple of mints which 'did their own thing ', presumably because that was what local merchants were used to. The standard type struck at the mint in Alexandria was the 12-nummi piece (marked I+B); there were also fractions – 6-nummi (S) and 3-nummi (Γ) – and also a 33-nummi coin (ΛΓ).
Thessalonica under Justinian I used yet another different standard, and you find a series of 16-nummi issues, marked on the reverse AISP or similar. The two middle letters IS stand for the number 16. There are also fractions: 8-nummi (AHP) and 4-nummi (AΔP). There are various theories about what the surrounding AP letters might mean.
And there was a minor mint at Cherson in the Crimea, producing coins apparently for local circulation, which didn 't follow the denominational marking system. But judging by size and weight, the Cherson issues were probably pentanummia.
That covers the start of the Byzantine era, where many collectors begin. If you can contribute to expanding this article - please do!
M or m = 40 nummi = follis
h = 8 pentanummium = follis (Maurice Tiberius, Cherson)
ΛΓ = 33 nummi (Alexandria)
Λ = 30 nummi
K = 20 nummi = 1/2 follis
IS = 16 nummi (Justin I, Thessalonica)
IB = 12 nummi (Alexandria)
I = 10 nummi = decanummium
H = 8 nummi (Thessalonica)
S = 6 nummi (Alexandria)
Є or Э = 5 nummi = pentanummium
Δ = 4 nummi (Thessalonica)
Γ = 3 nummi (Thessalonica)
NƆ = 2 1/2 nummi
B = 2 nummi (Thessalonica, Carthage)
T = 1 1/2 nummi (Thessalonica)
A or N = 1 nummus
MH = 48 nummi
XII = 12 nummi
XLII = 42 nummi
XXI = 21 nummi
IIII = 4 nummi