How cool is this?! Post anything you feel is relevant! Julia Mamaea, AD 222-235. Roman provincial Æ 28.5 mm, 11.90 g, 5 h. Ionia, Ephesus, AD 222-235. Obv: IOVΛIA MAMAIA CЄB, draped bust, right, wearing stephane. Rev: EΦЄCIΩN ΠΡΩTΩN ACIAC, Artemis driving biga of stags right, holding bow and drawing arrow from quiver. Refs: RPC VI, 4975 (temporary); Karwiese 804; SNG von Aulock --; SNG Copenhagen --. Notes: Ex-Plankenhorn Collection of Ionian Coins, ex-Naumann Auction 91, lot 927, 7 May, 2020.
You're right! Good eye! Triga, maybe? A die-engraver who couldn't count? It IS a biga on other examples, though.