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
(2) 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