Interesting coin there, Pendrak - and a definite attribution challenge. Maybe unpublished? Are there signs of an overstrike? Hard to tell from the pics - do all the letters seem to be from one strike? I don't know what it may be, but just to share my initial thoughts, although they're probably way off base:
I wonder if perhaps this is an issue, maybe unpublished, from Pisidia - maybe either Termessos (more likely) or Isinda - or from the general region. Both cities issued AE's with beaded-border Zeus obverses and galloping horse reverses - although Isinda's horses seem to have all had riders, and that city's Zeus' seem to have always been right-facing. On the other hand, Termessos' horses were left-facing (unlike yours), but they did issue some left-facing Zeus' - although with letters in the obverse fields.
Both cities issued coins with reverse legends reading from inside-out, that featured, like the OP coin, omega-nu (ΩΝ) combos (in the case of Termessos coins it was part of TEPMHCCEΩN or TEPMHCEΩN).
Sometimes on the Termessos issues the omega read correctly, oriented with the other letters from the inside-out, as on this obverse (and on the OP coin):

In other instances, the Termessos omegas were retrograde in relation to the other letters, as in the upper example in this set (the lower coin is an Isinda issue, with the omega oriented correctly):

Again, I really have no idea - but, for comparison, here are other Termessos issues:
http://coinproject.com/coin_detail.php?coin=206459http://www.forumancientcoins.com/ca...sp?zpg=26056https://www.vcoins.com/en/stores/sp...Default.aspxEdit: I should add that I like the similarity in the neckline (the line at the base of the neck) on the obverse portraits of the Termessos issues in comparison to the OP coin.