There's a bull (?) leaping/charging right and some readable letters above it, so it is probably possible to find the ID. Someone else wanna give it a shot? @paschka, can you help us out by providing the weight or diameter?
https://www.acsearch.info/search.html?similar=3198733 Thessalonica, Macedonia, AE20, 5.80 gr. 187-31 BC. Obv: OMONOIA, veiled and diademed head of Homonoia right. Rev: QES-SALON-RWN above and beneath horse running right. Moushmov 6621; SNG Cop 378: Mionnet I, 341. Contributed by Ii.JJ, November 2011. http://www.wildwinds.com/coins/greece/macedonia/thessalonica/Moushmov_6621_2.jpg
MACEDON THESSALONICA Bronze. Autonomous under Roman rule. Circa 187-168/7 BC. 19 mm. 6,91 g. Obv: Veiled and diademed head of Homonoia right. Rev: Horse galloping right. SNG ANS 806. VF http://www.ebay.de/itm/LANZ-MACEDON...G1XTibERwPriIW%2Ft2Xg%3D&orig_cvip=true&rt=nc Rare
Not sure how you're getting those letters out of what can be seen on your coin's reverse, plus that's a bull rather than horse. Visible letters on your coin's reverse: A M Φ(looks more like an O but probably phi) I Π = Amphipolis Here's an example from Wildwinds: Macedonia - Amphipolis Circa 187-31 B.C. AE 17 mm. 6.450 grams. Obverse: Head of Artemis r.; at her shoulder, bow and quiver. Reverse: Bull bounding r. SNG C 72 (Moushov 5978)
