While I own a couple much nicer tets from this king, I'm still happy to have this auction win. Just found out about the win today - and, I must admit, it was a surprise since I totally forgot that I had even placed a bid - and a relatively low one at that. Dealer's B/W pic below; coin en route.
It has issues - shall we say: character traits - such as graffiti in the obverse field, wear, some deposits and porosity. Still, overall it's a respectable example and, at 30mm, of decent size. The coin, which was struck in December of 26 BC, becomes my second "ex-Nisa Collection" acquisition.
Anyone who is into stories of historical betrayal, intrigue, family incest, murder, and such would likely be interested in the story of how this guy was poisoned by his Roman ex-concubine/slave wife Musa and their son Phraataces (who was also Musa's - his own mother's - lover....ewww!). After Phraates IV's murder, Musa married her son, who ruled Parthia for several years until overthrown by Orodes III.

Phraates IV
Ruled circa 38/7-2 BC; coin dated Audynaios SE 287 (December 26 BC)
BI Tetradrachm (30mm, 14.05 g, 12h)
Seleukeia on the Tigris mint
Obv: Diademed bust left
Rev: Phraates seated right, receiving palm from Tyche standing left, holding cornucopia
Sellwood 51.25
From the Nisa Collection.