The Semis denomination
The semis ('half') was a small Roman bronze coin that was valued at half an as. During the Roman Republic, the semis was distinguished by an 'S' (indicating semis) or 6 dots (indicating a theoretical weight of 6 uncia).

Some of the coins featured a bust of Saturn on the obverse, and the prow of a ship on the reverse.

Initially a cast coin, like the rest of Roman Republican bronzes, it began to be struck from dies shortly before the Second Punic War 218-204 BC.

The coin was issued infrequently during the Roman Empire, and ceased to be issued by the time of Hadrian 117-138 AD.
Semis
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An AE Semis struck 38-37 BC in Syria
Obverse: M•ANT•TER•COS•DES• ITER•ET•TER•III•VIR•R•P•C, bare head right.

Reverse: L•BIBVLVS•M•F•PR•DESIG, quinquereme right, with three oars and stern ending in boar's head left.

Diameter: 20 mm
Die Orientation: 0 H
Weight: 3.61 g

Provenance: Private purchase (May 2018).

RPC I 4092
(2) Rome
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An AE Semis struck 211-208 BC in Sicily
Obverse: laureate head of Saturn right; S

Reverse: prow of galley with corvus right; grain ear above; S / K / ROMA

Diameter: -
Die Orientation: -
Weight: -
No notes for this coin
Crawford 069/03a; Sydenham 310b; Type as RBW 287
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An AE Semis struck 211-206 BC in Rome
Obverse: laureate head of Saturn right S

Reverse: prow of galley right S ROMA

Diameter: -
Die Orientation: -
Weight: 18.6 g
No notes for this coin
Crawford 056/03, McCabe G1