Hi. Despite the poor condition of this ancient coin, I think it would be better to identify it since it has a clear counterstamped lettering. It could be Sassanid or Arab Byzantine ? Thank you for this hard task. Charles
Islamic counterstamp at least. One cannot tell if the host coin is a Byzantine coin, or an imitative Byzantine coin.There is nothing Sassanid about the host coin in my eyes, unless you are talking Sassanid-Byzantine coins minted around 620 when the Sassanids took over Syria and struck their own imitations of Byzantine bronzes.
I don't see a countermark? The coin is a dirhem of Nur al-Din Mahmud of the Zengids in Syria. Aleppo mint.