An "uncia" (plural: unciae) was the twelfth part of the Roman pound ("as" or "libra").  Although when Rome first began bronze coinage in the early third century BC the "uncia" was produced at full weight (about 27.25 grams), by the time of the great Republican coinage reform of 211 BC it was down to about 10 grams.  By 108 BC the bronze was being issued on the "uncial" standard where the "as" was struck at the weight of an uncia, and the uncia was 1/12 of its original weight, or about 2.3 grams.  The bronze was reduced even further about 90 BC when the "lex Plautia Papiria" established the "semuncial" standard where the "as" was struck at about half of a Roman ounce (or about 13.6 grams), and the uncia was again reduced proportionately to just over 1 gram.  The Republican unciae were discontinued very shortly after the passage of the "lex Plautia Papiria".

In Imperial times the bronze roughly followed the "semuncial" standard, with the "as" being struck under Augustus at about 11-13 grams.  Its weight stayed relatively constant throughout the first and second centuries at about 10.75 grams.  The smallest Imperial bronze normally stuck was the "quadrans," a coin equal to three uncia or a quarter of an "as," and struck at between 2.8 and 3.0 grams

However under Hadrian (117-138) the uncia was revived briefly, being struck at a weight of slightly less than 1.0 gram and at about 10 millimeters in diameter.  The name "uncia" has been applied to this coin since it is plainly meant to have been 1/12 of an "as" and hence an "uncia".  Their extremely small size only allowed Hadrian's bust on an anepigraphic obverse, and the only reverse design is "S C" within a wreath.  The new unciae were discontinued before the end of Hadrian's reign.


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Uncia (ounce), a brass coin, the twelfth |part| of a Roman pound, or As [AS]. The issue of an As of a Roman pound of 12 unicae, or the as libralis, took place in the time of the Decemvirs, 451 BC, but the existing asses rarely weigh more than 10 unicae. Later the As fell successively from 10 unicae to four, or perhaps this reduction was suddenly accomplished about the time of the first Punic War, 268 BC. In 217 BC the As was reduced to one unica by the Lex Flaminia. At last in 89 BC or thereabouts, under the Lex Papiria, the As fell to a semuncia (half-ounce). The uncia was rarely struck after the reduction of the As. The expression heres ex uncia denoted the heir to a tenth or twelfth |part| of an estate. The mark of value of the uncia was (a dash-like symbol -); of the semunica S. Among the pieces struck at Paestum there occurs the Sescuncia (semisqueunica -S) equal to the eighth of an As.

The principal types of the earliest uncia, semuncia, and aes grave of Italy are:
- Knuckle-bone
- Acorn
- Grain of barley
- Vase
- Club
- Frog
- Spear-head
- Ear of corn
- Crescent
- Head of Apollo or Diana
- The Dioscuri
- Hercules
- Lion
- Boar's head
- Owl
- Axe with two edges (double axe or bipennis)
- Shell
- Anchor
- Thunderbolt (fulmen)
- Gaulish head
- Prow of a ship
- Two-handled vase
- Amphora
- Anchor
- Sacrificial knife
- Hatchet

The ordinary kind of uncia is: Obv. Helmeted head left, - behind. Rev. Prow of a vessel to right, - below; bronze, but the following are types other than "prow of a ship" issued at Rome after the suppression of the as libralis in 268 BC:

1st Period, 268-224 BC

- Obv: Helmeted female head, - behind. Rev: A cornucopiae (rare); bronze.
- Obv: Female head with Phrygian helmet terminating in the beak of a bird. Rev: One of the Dioscuri galloping; bronze.
The semuncia (S ) has on the obverse the heads of the Dioscuri, and on the reverse two horses galloping, two stars above.
- Obv: Female head right, - behind. Rev: SAR (Saranus), elephant to left.
  The moneyer may have been M. Atilius Serranus, who, in 190 BC, was, with two other praetors, L. Valerius P.F. Flaccus and L. Valerius C.F. Tappus, named IIIVIR Col. Ded. (triumviri ad colonos deducendos, Liv. xxxvii, 46, 57), or perhaps another of the same family, who was praetor in 174 (Liv. xli, 21.)
- Obv: Female head. Rev: A CAE (Aulus Caecilius) within a wreath; bronze.
No mark of value on this uncia. Coins with this legend are usually attributed to Caecina gens, but it is thought that A. Caecilius is the aedile of 189 BC.
2nd Period, 154-134 BC:

- Obv: Helmeted female head right, - behind. Rev: L H TVB (in monogram; Lucius Hostilius Tubulus) within a laurel wreath; in the exergue ROMA; bronze.
  This person is probably L. Hostilius Tubulus, who was praetor in 142 BC. and exiled the following year.
3rd Period, 134-114 BC

- Obv: Helmeted female head right, - behind. Rev: Q METE (in monogram; Quintus Metellus) within a laureal wreath; in the exergue ROMA; bronze.
  This Metellus is probably one of three from the Caecilia gens, who was consul in 123, 109, and 98 BC.
4th Period, 114-104 BC

- Obv: L PHILIPPVS, laureate head of Saturn; sometimes a sickle behind. Rev: Dog walking to right, - above; sometimes a prow of a vessel, dog and - above; bronze.
  This person is probably the son of the moneyer Q. Philipus (109 BC.), and was monetary triumvir about 112.
- Obv: Helmeted |bust| of Minerva (?), - behind. Rev: Q LVTATI (Quintus Lutatius) within an oak wreath; bronze.
  Unknown person. Date about 104 BC.
- Obv: Helmeted female head right, - behind. Rev: C FON (Caius Fonteius), Mars in a quadriga to right; in the exergue ROMA; - above; bronze.
  This person is perhaps the Fonteius who perished at Asculum in 91 BC.
- Obv: CN DOMI (Cnaeus Domitius), diademed head of Venus right, - behind. Rev: Q CVRTI M SILA (Quintus Curtius. Marcus Silanus), a lyre; bronze.
  Q. Curtius is unknown, but perhaps was the father of Q, Curtius, who was iudex quaestionis in 70 BC. M. Silanus was probably the son of M. Junius D.F. Silanus who was Consul in 109.

5th Period, 104-84 BC
- Obv: Helmeted female head right, - behind. Rev: M HERENNI (Marcus Herennius) ROMA, two cornuacopiae; bronze.
  This person is perhaps the son of the Consul of 92 BC.
- Obv: Helmeted female head right, - behind. Rev: MAN (in monogram) FONT (Manius Fonteius) ROMA, a quadriga; bronze.
  This person is perhaps the quaestor in 84 BC.
- Obv: SCAEVA, helmeted head of Pallas (?) right. Rev: M AVF (in monogram; Marcus Aufidius), Centaur right; bronze.

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