The Tritartemorion denomination
The tritartemorion was an ancient greek coin denomination worth 3 tartemoria - and weighing roughly 0.54 grammes.

The name comes from 'tetarton', meaning a fourth, and 'morion' meaning part. So it is literally a 'three-quarters-part'.
Tritartemorion
(1) Mende
/Files/Images/Coinsite/CoinDB/Mende.jpg
An AR Tritartemorion struck c. 460-423 BC in Mende
Obverse: ass standing right

Reverse: crow standing right within incuse square

Diameter: -
Die Orientation: -
Weight: 0.5 g
No notes for this coin
SNG ANS 354
(2) Thasos
/Files/Images/Coinsite/CoinDB/Thasos_-_diobol.jpg
An AR Tritartemorion struck 411-404 BC in Thasos
Obverse: head of Satyr left

Reverse: two dolphins - upper to the left, lower to the right; ΘAΣI

Diameter: -
Die Orientation: -
Weight: 0.4 g
No notes for this coin
SNG Cop 1033-1034; Le Rider 12; HGC 340; Beoetia p. 52. Traité III, 347. BCD Boiotia 280