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.
Half-Follis
(1) Claudius II
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An AE Half-Follis struck 318-319 AD in Thessalonica
Obverse: veiled laureate head right; DIVO CLAVDIO OPTIMO IMP

Reverse: emperor seated left on curule chair, holding short scepter, raising right hand; REQVIES OPTIM_ORVM MERITORVM / •TS•A•

Diameter: -
Die Orientation: -
Weight: 1.2 g
struck by Constantine I
RIC VII Thessalonica 26
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An AE Half-Follis struck AD 337-340 in Antioch
Obverse: DV CONSTANTINVS PT AVGG, veiled head right

Reverse: Constantine driving galloping quadriga heavenward, holding reins with left hand and raising right hand upwards to grasp Manus Dei, which reaches down from above; star in upper left field, SMANE in exergue

Diameter: 15 mm
Die Orientation: 5 H
Weight: 1.73 g
Struck under Constantius II
RIC 37; Sear 17488
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An AE Half-Follis struck 318-319 AD in Siscia
Obverse: Veiled laureate head right; DIVO MAXIMIANO SEN FORT IMP

Reverse: Emperor seated left on curule chair, holding short scepter, raising right hand; REQVIES OPTIM_ORVM MERITORVM / SIS

Diameter: -
Die Orientation: -
Weight: 1.16 g
struck by Constantine I
RIC VII Siscia 41
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An AE Half-Follis struck 309-312 AD in Ostia
Obverse: DIVO ROMVLO N V BIS CONS, Bare head of Romulus facing right

Reverse: AETERNAE MEMORIAE, Domed shrine with one door open, eagle standing facing right on roof; MOSTP in exergue

Diameter: 22 mm
Die Orientation: 6 H
Weight: 3.82 g
No notes for this coin
RIC VI Ostia 59