For what it's worth (not much, probably): Working on a theory that the degraded legend may include a HΣI sequence (see detail below), it might be an Odessos issue with Zeus obverse and an off-center and corroded horseman/monogram/OΔHΣITΩN reverse.

The size would be right. For comparison, with the OP coin in the mix:


The size would be right. For comparison, with the OP coin in the mix:






















