The 1/3 Stater denomination
The Stater was an ancient Greek or Lydian denomination, which circulated from the 8th century BC to AD 50.

The silver staters minted at Corinth weighed 8.6 grammes, and was divided into three silver drachmae of 2.9 g. It was roughly equivalent to the Athenian didrachm, which weighed 8.6 g.

The 1/3 Stater was correspondingly a denomination worth a third of a stater. It was struck in both gold and silver.
1/3 Stater

(1) Perikles 380-360 BC
Obverse: lionskin facing
Reverse: triskeles, laureate bust of Apollo facing ΠEP_IKΛE (in lycian script)
Ref: SNG Copenhagen -; SNG v. Aulock -. ...