Great! that matches the measures for a Drachm. The two dominant coins of Alexander were the drachm and the tetradrachm. The drachm is about 18 mm wide and weighs about 4.2 grams of silver. Yours is a little less due to the loss of metal one can see on the obverse (behind the head). Nevertheless, it is a beautiful coin. Thank you very much for sharing I guess it looks even better in the hand than on the picture. Congrats and enjoy