The Uncia denomination
The uncia ("twelfth part") was a Roman denomination worth 1/12 of an as.

Obverse types of the uncia include a knucklebone (c. 289–245 BC), a barleycorn (c. 280–245 BC), and the helmeted bust of Roma (from c. 240 BC).

In imperial times the uncia was briefly revived under Trajan (98–117) and Hadrian (117–138). This coin was about 11–14 mm in diameter and weighed about 0.8–1.2 grams. It featured the bust of the emperor on the obverse with no inscription and "SC" (for Senatu Consulto) in a wreath on the reverse.
Uncia
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An AE Uncia struck 217-215 BC in Rome
Obverse: Helmeted head of Roma left, pellet behind.

Reverse: Prow right, ROMA above, pellet below.

Diameter: 25 mm
Die Orientation: 12 H
Weight: 11.16 g
No notes for this coin
Crawford 38/6, Sydenham 86.
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An AE Uncia struck 217-215 BC in Rome
Obverse: head of Roma left wearing crested Corinthian helmet ●

Reverse: prow of galley right ROMA ●

Diameter: -
Die Orientation: -
Weight: 12.6 g
No notes for this coin
Crawford 38/6, SRCV I 615, Sydenham 86, BMCRR 88, McCabe group AA semilibral