This looks to be an "artistic impression" of a Syracuse Dionysius, which was a coin made around 480 BC. A kind person has reached out to let me know this is a piece by artist Harris G Strong.
The frame is approximately 16" vs 17" and the "coin" itself is approximately 5" across.
I believe this was framed in 1990 according to a small inscription on the frame.
The Arethusa I had in the same style sold within a day, so don't wait too long on this one!