Watch List notes:

THRACE. Mesembria. Mid-late 5th century BC. Obol (Silver, 7.5 mm, 0.52 g). Head of a warrior facing, wearing a Corinthian helmet. Rev. Irregular quadripartite incuse square. SNG BM 265. SNG Stancomb 217. A curious little coin, struck on a flan designed to emphasize the helmet on the obverse. Toned. Some surface roughness, otherwise, good very fine.
From the "Collection sans Pareille" of Ancient Greek Fractions, ex Aufhäuser 5, 5 October 1988, 35.