Watch List notes:

Greek Coinage

Kings of Pergamum. Tetradrachm, circa 263-241 BC, AR 16.89 g. Laureate head of Philetairos r. Rev. Athena seated l., holding wreath and resting l. elbow on shield set at her side.; in outer l. field, ivy-leaf. In inner l. field, A and in r. field, bow. Westermark group V (Attalos I). For a reattribution to the latest reign of Eumenes I, see Meydancikkale pp. 334-338
Nicely toned and with a wonderful portrait. Some porosity on
reverse, otherwise extremely fine

Ex ACR sale 8, 2014, 227.
The coinage of the Attalids is an extremely conservative one as it honors the eunuch Philetairos, treasurer to Lysimachos and founder of the Attalid dynasty, by invariably strucking in his name.
Differentiating the issues of the kings is therefore quite a difficult task as it depends upon the various subsidiary symbols, monograms, and other details on the coins (as noted in Westermark's survey of the kingdom's coinage), with a few later modifications, particularly those noted in the analysis of the Meydancikkale hoard.
As a matter of fact, though Westermark places this issue relatively late in the series, its refined and elegant style - probably the most pleasing to be found in the entire series – combined with new hoard evidence has brought it back to the latest reign of Eumenes I.