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
An AE Onkia struck 420-405 BC in Kamarina
Obverse: Gorgoneion with smooth neat hair tied with ribbon protruding tongue

Reverse: owl standing left, head facing, lizard in right talon; KAMA / B / •

Diameter: 12.5 mm
Die Orientation: -
Weight: 1.4 g
No notes for this coin
Calciati vol III, p. 53, 15; SGCV I 1064 var; Jenkins 186; CNS III, 13.