Watch List notes:

Thrace, Byzantion AR Tetradrachm. In the name and types of Alexander III of Macedon. Re-tariffed circa 235-225 BC. Head of Herakles right, wearing lion skin headdress; countermark: BY above prow, all within incuse circle / Zeus Aëtophoros seated left, holding sceptre; [Α]Λ[ΕΞΑΝΔΡΟΥ] to right, control marks not visible. For countermark: Propontis 144; for discussion see Price pp.69-70. 16.75g, 26mm, 1h.

Very Fine - Good Fine. Test cut to obv. Very Rare with this countermark.

During this period, autonomous coinage was introduced in Kalchedon and Byzantion including a lighter weight tetradrachm of approximately 13.9g. The heavier tetradrachms remaining such as this one were countermarked and continued circulating.