Watch List notes:

SICILY. Messana (as Zankle). Circa 525-494 BC. Hemilitra (Silver, 11.5 mm, 0.28 g). DΑ Dolphin swimming to left within the crescent-shaped harbour of Zankle. Rev. Nine-part incuse divided into equal squares, some raised, some lowered and some diagonally divided; at the centre, scallop shell. Buceti 5c. Gielow -. HGC 2, 769 (this coin). Cf. SNG Fitzwilliam 1063 (litra). Extremely rare, one of the few known examples of this denomination from Zankle. Nicely toned and with a splendid obverse. Reverse weakly struck with traces of corrosion, otherwise, extremely fine.
From the "Collection sans Pareille" of Ancient Greek Fractions, and from the collections of R. Maly, LHS 100, 23 April 2007, 165 and A. D. Moretti, Numismatica Ars Classica 25, 25 June 2003, 82 (but there termed an obol).