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

(1) Augustus 27 BC-14 AD
Obverse: AVGVSTVS DIVI F, Head of Augustus facing left, wearing laurel wreath
Reverse: CAESAR AVGVSTA L CASSIO C VAL FEN, Vexillum on base; II VIR to left and right
Ref: RPC I 311
(2) Castulo c. 200-175 BC
Obverse: Diademed head right
Reverse: Bull right, crescent above; KASTILO retrograde in southern hispanian script
Ref: CNH p. 331, 2-3; SNG BM Spain 1223-...
(3) Decius AD 249-250
Obverse: IMP C M Q TRAIANVS DECIVS AVG, laureate, draped and cuirassed bust right
Reverse: Mars standing left, holding shield and spear; S C across field
Ref: RIC 128; Sear 9433
(4) Germanicus 15 BC - 19 AD
Obverse: Bare head left; GERMANICVS CAESAR TI AVG F
Reverse: Aquila between two standards; MVNIC__ITALIC / PE_R / AV_G
Ref: RPC I 70; ACIP 3339
(5) Iaitos c. 241-30 BC
AE Semis Iaitos
Obverse: helmeted head of warrior righ
Reverse: warrior standing half-left, with grounded spear and shield; IAITI_NΩN
Ref: CNS I pg. 383, 4; SNG ANS -
(6) Marcus Antonius 38-37 BC
AE Semis 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.
Ref: RPC I 4092
(7) Nero 65 A.D.
Obverse: NERO CLAVD CAESAR AVG GERMA, bare head right, with globe at point of bust.
Reverse: CER QVINC ROM CON around, SC in exergue, Table, seen at an angle, surmounted by an urn on the left and wreath on the right.
Ref: RIC 488
(8) Parion c. 45 BC
Obverse: female head right wearing stephane; C_G / I_P
Reverse: praefericulum; D_D
Ref: RPC I 2259; SNG France 1416
(9) Rome | Anonymous 211-206 BC
Obverse: laureate head of Saturn right S
Reverse: prow of galley right S ROMA
Ref: Crawford 056/03, McCabe G1
(10) Tiberius 12-14 AD
Obverse: TI CAESAR AVGVST F IMPERAT VII, Head of Tiberius facing right, wearing laurel wreath
Reverse: Altar of Lugdunum, ROM ET AVG below
Ref: RIC I (Second Edition) Augustus 246