The Onkia denomination
The Onkia is an ancient Greek denomination based on the Sicilian standard. In silver it weighs 0.07 grammes - but it was (exclusively?) struck in base metal.

The Onkia was worth 1/12th of a Litra, another Sicilian denomination, and has given name to the Roman Uncia, the Ounce, and the Inch, which are all 1/12ths of something.

(1) Kamarina 420-405 BC
Obverse: Gorgoneion with smooth neat hair tied with ribbon protruding tongue
Reverse: owl standing left, head facing, lizard in right talon; KAMA / B / •
Ref: Calciati vol III, p. 53, 15; SGCV I...