Egypt. Alexandria. Antoninus Pius, 138-161. Drachm (Bronze, 33.90 mm, 26.59 g). Dated RY 21 (= 157/8). ΑΥΤ ΚΑΙ Τ ΑΙΛ ΑΔΡ ΑΝΤ[ΩΝΙΝΟϹ ϹΕΒ] ΕΥϹ Laureate head right. Rev. Isis-Sothis, seated facing and holding a cornucopia and scepter, riding a dog (Sirius?) right, wearing a radiate crown and is looking back at Isis; below L / KA (date) across field. Geissen 1804 var. (obv. bust type and date position). Dattari-Savio 2681 & 8581 var. (same). Emmett 1593 var. (same). RPC IV.4, 1982.12 (this coin). Rough dark patina. Good Fine. Rare. Ex Giovanni Dattari Collection, 2681. Ex Naville Numismatics Ltd. 45, 09.12.2018, lot 310. 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.