The Hemiassarion denomination
The hemiassarion was a bronze denomination worth ½ as - assarion in Greek.

It was commonly struck by Roman Provincial mints, and was not struck to a standard weight but rather to some local standard. It was simply a coin worth ½ of the local basic coin denomination.
An AE Hemiassarion struck 138-161 AD in Antiochia ad Maeandrum
Obverse: ΑV ΚΑΙ ΤΙ ΑΙΛ ΑΔ ΑΝΤΩΝƐΙΝOC, laureate head of Antoninus Pius, r.

Reverse: ΑΝΤΙΟΧƐΩΝ, Nike advancing, r., holding wreath and palm-branch

Diameter: 17 mm
Die Orientation: 12 H
Weight: 3.3 g
Leu Numismatik is calling the metal bronze and the denomination Hemiassarion:
RPC Online IV.2, 816 (temp); BMC 34–5; Cop 51
An AE Hemiassarion struck 138-161 AD in Philippopolis
Obverse: ΑΥ Τ ΑΙ ΑΔΡΙΑ ΑΝΤΩΝΕΙΝΟϹ, Head of Antoninus Pius facing right, wearing laurel wreath

Reverse: ΦΙΛΙΠΠΟΠΟΛΕΙΤΩΝ, Ares (or Protesilaos) advancing left, holding shield

Diameter: -
Die Orientation: -
Weight: -
CC Vermeule suggests the figure is Protesilaos instead of Ares because: "The hero Protesilaos was particularly venerated in Thrace and Thessaly. He was the first Greek to fall at Troy. Vermeule associates such figurative depictions on coins like this one with the Riace bronzes and justifies his identification of the figure with Protesilaos with the fact that Protesilaos, as the founder of the city, points to the ground, while Ares would adopt a fighting stance ("The God of war on the Borghese statue ... does not point downwards""
Varbanov 747; RPC Online IV.1, 7445 temp.
(3) Geta
An AE Hemiassarion struck 198-209 AD in Marcianopolis
Obverse: draped bust right from behind; Π CEΠTI_ΓETAC K

Reverse: tripod, snake entwined around leg; MAPKIANO_ΠOΛITΩN

Diameter: 17 mm
Die Orientation: -
Weight: 1.74 g
No notes for this coin
Varbanov I 1117; AMNG I/I 703