Arab Sasanian, Eastern Sistan Series, Rida رضا (Probably AH 153s / AD 780s), AR drachm.
3.39gm, 32.2mm. Mint SK (Zaranj Eastern Sistan) year probably AH 153s / AD 780s.
Sasanian style bust right, "Bism Allah Rabbi [Salih] Rida" ( بسم الله ربي [صالح] رضا) in Arabic around margins / Fire altar with attendants.
Zeno-345405 (It's me there), Album-89D. Good very fine, natural patina. Very Rare.
Notes:
According to Stephen Album, 3rd edition, PAGE 32
It is probable that the word salih is not part of the name but rather some sort of title.