The Half-Follis denomination
The half-Follis was a Roman Imperial and Byzantine denomination valued at, well, half a follis.

It was struck only infrequently, mostly in the years the Diocletian coin reform in 294 AD and before the shrinking follis made the half-follis impractical.

When the Follis was reintroduced by Anastasius in 498, the half-follis was also reintroduced. It was valued at 20 nummi and marked with a large 'K' for 20.
An AE Half-Follis struck 593 AD in Constantinopolis
Obverse: D N MAVR TIBER PP AV. Helmeted and cuirassed bust facing, holding globus cruciger and shield.

Reverse: Large mark of value K; ANNO to left, cross above, X/I to right, A in exergue.

Diameter: 22 mm
Die Orientation: -
Weight: 5.15 g
1st officina. Dated RY 11.
SBV 497; DOC 56a