Watch List notes:

Kingdom of Pergamon, Philetairos I AR Tetradrachm. Circa 270-265 BC. Diademed head of the deified Seleukos I to right / Athena, helmeted and wearing long robes, seated to left on low throne with lion's feet, resting her left elbow on support, holding a transverse downward pointing spear in her left hand and resting her right on the edge of a round shield standing before her adorned with a gorgoneion; attic helmet above, crescent in exergue. SC 309.1; Newell, NNM 76, 9; Ingvaldsen, Florilegium Westermark, p. 177, 1. 16.70g, 30mm, 12h.

Good Fine. Extremely Rare with Attic helmet symbol; no examples on CoinArchives.