Byzantion, Thrace. AE21 civic issue. ca 240-220 BC. 5.9 g. Magistrate Dioskoy.
 
Diademed head of Poseidon right. 
PY (ligate) EPI DIOSKOY downwards to right and left of filleted trident with dolphin to left and right.

BMC 32; Schönert-Geiss, Byzantion 1044ff; SNG Black Sea 63; SNG Cop 490; Hoover HGC 1417; Pozzi 2424; Prokesch-Osten 15 in NZ 4. 

PY ligate is the monogram of Byzantion.

With permission of Numismatik Naumann auction 66, Lot 49, June 2018.