I saw you'r coin and got out my copy of the Wayne G Sayles book volume 6 non-classical cultures To me it looks like the Sabaens where
imitative of the Athenian tets. But the book says " In addition to the classical imitations of Southern
Arabia, a similar phenomenon may be seen in the region of the Persian Gulf ( or the northern
part of the Arabian Sea). The billion tetradrachms struck by Abi'el an obscure ruler in this region where modelled after the earlier tetradrachms of
Alexander the Great. " The dateing is given as ca. 2nd-1st century B.C. I haveseen Sabaen and Himyarite coins on sale often but never have seen this, on the market, you got a
good buy. I
hope this helps