Thrace, Islands off, Thasos. Circa 435-411 BC. AR 9.7mm obol 0.5 g. 

Two dolphins, one above the other, swimming in opposite directions, two dots below.
Quadripartite incuse square. 

BMC 18-22 (Thrace), Moushmov 5647; Le Rider, Thasiennes 9; HGC 6, 337.

With permission of Eidmar auction 3, lot 22 (on biddr.com), March 2024.