Stumper, Steve. I have no clue on this one. I do know it's not Elymaean or Parthian, though. I see how you are interpreting the obverse(?) as a helmeted bust, but I'm not entirely certain about it. The garb - tunic? - with its downward-facing points, along with the figure's short legs, kind of reminds me of some South Asian Kushan, earlier Ujjaini, and later Kushano-Sasanian depictions of standing figures - particularly Vasudeva issues.
Clearly it's not Kushan - it's too thin, there's no altar, no nimbus, etc. Maybe an unpublished local issue from the general time of the later Kushan Empire? I could be hundreds of years and thousands of miles off...I'm just brainstormin' here, sharing the first things that come to mind. Unfortunately no time to hunt...finishing up the first week of classes...very busy week. Some Vasudeva's with the OP coin below.

Clearly it's not Kushan - it's too thin, there's no altar, no nimbus, etc. Maybe an unpublished local issue from the general time of the later Kushan Empire? I could be hundreds of years and thousands of miles off...I'm just brainstormin' here, sharing the first things that come to mind. Unfortunately no time to hunt...finishing up the first week of classes...very busy week. Some Vasudeva's with the OP coin below.























