PTOLEMAIC KINGS OF EGYPT. Ptolemy II Philadelphos, 285-246 BC. Tetradrachm (Silver, 26 mm, 13.82 g, 1 h), Alexandria. Diademed head of Ptolemy I to right, wearing aegis around neck; on neck, countermark: monogram of ΔI within ΠY; all within round incuse. Rev. ΒΑΣΙΛΕΩΣ - [ΠΤΟΛΕΜΑΙΟΥ] Eagle, with closed wings, standing left on thunderbolt. Cf. Svoronos 548. Darkly toned. Fine.

The obverse countermark was applied by the city of Byzantion sometime in the late 3rd century, possibly as a measure to revalidate the Ptolemaic weight standard tetradrachm as equal to the city's own civic tetradrachms of Attic weight. Parts of Thrace had been in Ptolemaic possession since the early 3rd century and the Ptolemaic coinage therefore played a significant role in the whole region