undetermined countermarked Greek coin

Abydos in Troas(?), Bithynia, time of Prusias I (?), 229-183 BC.(?),
Æ 24 (23-25 mm / 10,37 g), bronze, axes medal alignment ↑↑ (ca. 0°),
Obv.: head of Artemis right, bow and quiver at shoulder behind, rectangular countermark on neck: chelys (lyre).
Rev.: …AN TPHN… (?) , eagle standing right, wings open; A.. -monogram in upper left field.
for countermark: cf. Howgego (GIC) 420-23. (all different) .