A bit of a follow-up, Jeff. I'm providing links to what might be a double die match to your Orodes I/Mithradates III drachm, this one from the Todd A. Ballen Collection. It now resides in the Schatz Collection, which gives that little coin double-great provenance/pedigree. Schatz has the most extensive collection of Parthian coins that I know of.
While the CNG listing acknowledges the "unusual style," it doesn't speculate about the possibility of it being a contemporary imitation. I do still think that it
might be an ancient counterfeit. But, on the other hand, there were indeed some weird looking official coins in Parthia too. Generally, those came from Eastern mints, not from Ekbatana. The mint on your coin seems to be uncertain.
https://cNGCoins.com/Coin.aspx?CoinID=153336https://www.forumancientcoins.com/g...=6590&pos=12