Egypt. Alexandria. Antoninus Pius, 138-161. Drachm (Bronze, 32.50 mm, 16.94 g). Dated RY 21 = AD 157/8. ΑΥΤ Κ T ΑΙΛ AΔP ΑΝΤωΝΙΝΟϹ [CЄB ЄYC] Bare-headed and draped bust right. Rev. Isis-Sothis, seated facing and holding a cornucopia and sceptre, riding right on dog (Sirius) running right, head left looking back at Isis; below LKA (date). Geissen 1804 var. (obverse bust type and date position). Dattari-Savio 2681 & 8581 var. (same). Emmett 1593 var. (same). RPC IV, 4.1980.3 (this coin illustrated). Dattari-Savio Plate 136, 8581 (this coin). Emmett 1593. Green patina. Very Fine. Rare. From the Dattari Collection. Ex Naville Numismatics Ltd. 48, 07.04.2019, lot 279. On the myth of Isis-Demeter-Sothis that appears on the reverse of this rare drachm of the year 21 of Antoninus Pius (157-158 AD), compare the specific article by Staffieri G. M. in the journal "Annotazioni Numismatiche 30, Anno 8, giugno 1998, pp. 693-697, where an Antonine drachm of the same date and reverse scene of ours is reproduced, both from the Dattari collection. Isis in Greek-Egyptian theological syncretism is assimilated to the star Sothis, i.e. the Roman Sirius, the brightest star in the constellation of the Greater Dog: hence the visual meaning of the drachm's reverse.