EGYPT. Alexandria. Antoninus Pius, 138-161. Drachm (Bronze, 32 mm, 23.22 g, 12 h), RY 21 = 157/8. Α[ΥΤ Κ] Τ Α ΑΔ[Ρ ΑΝΤΩΝΙΝΟC CЄΒ ЄΥC] Laureate head of Antoninus Pius to right, with slight drapery on his left shoulder. Rev. [L KA] Isis-Sothis, holding cornucopiae in her right hand and scepter in her left, seated on dog (Sirius) leaping right, head to left and wearing radiate crown. Dattari (Savio) 8581. Emmett 1593.21. K&G 35.752 var. (differing bust type). RPC IV.4 online 15227. Very rare. Light deposits, otherwise, good fine.


This coin represents Isis as the Egyptian Sepdet (Sothis in Greek), a personification of Sirius, the brightest star in the firmament. Sirius' heliacal rising in mid-July heralded the coming of the Nile inundation, without which civilized life would be impossible in the scorching sands of Egypt. So important was this event to the Egyptians that the start of their civil calendar originally coincided with the heliacal rising of Sirius. However, although the Egyptian civil calendar only lasted 365 days, there are 365.25 days between two successive heliacal risings of Sirius. In other words, every four years, the civil calendar shifted by one day versus the “Sothic year”. After 1460 Sothic years, or 1461 civil years, the heliacal rising of Sirius again took place on the first day of the month Thoth (Egyptian New Year), and a Sothic cycle was completed. According to Censorinus (De Die Natali 21.10) such a cycle was completed in 139 CE, at the start of Antoninus Pius' reign.