It is a Balkan area Roman provincial "Koinon" issue under Gordian III or Severus Alexander depicting Alexander The Great and a legend showing his name. I can't make out the reverse, but this should give you plenty of clues to further research the coin.
Here's some that I found online. They match your coin to an extent. Gordian III Region: MACEDON Koinon Date: Time of Gordian III, 238-244 AD Denomination: Æ27 Weight: (10.61 gm) Obverse: Head of Alexander the Great Reverse: Alexander on horseback. References: SNG.Cop.1356. AMNG.647.
This coin comes in umpteen varieties and attributing mine was a bear! Time of Severus Alexander, AD 231-235. Quasi-autonomous AE 25.1 mm, 11.60 g, 7 h. Koinon of Macedon. Obv: AΛЄΞANΔPOV, diademed head of Alexander the Great with flowing hair, right. Rev: KOINON MAKЄΔONΩN NЄΩ, Alexander, his cloak fluttering behind him and raising right arm, galloping his horse, right. Refs: AMNG III 388; cf. BMC Macedonia p.24, 120; cf. Lindgren II 1374.