Another coin from my Ancient Greek collection.
This obverse type has been variously interpreted as representing the Dioscuri, the rising and setting sun, and the two branches of the river Danube. - Greek Coins and Their Values by David Sear.
This is an often faked coin type but here is a nice, genuine example.
Istros, Silver stater
Obv:- Facing male heads, left inverted
Rev:- ΙΣΤΡΙH, sea-eagle grasping a dolphin with talons, A below dolphin
Minted in Istros, 400 - 350 B.C.
Reference:-- AMNG I 416, SNG Cop 192 var (right head inverted), SGCV I 1669

Regards,
Martin