ROMAN EGYPT/Antoninus Pius CE 138-161

AE Drachm, 34 mm, 20.64 g, 11h, Alexandria mint, Regnal Year 13/CE 149-150

Milne 2054 var.
Emmett 1621 var.

O: laur draped bust right, AVTKTAIΛAΔP/ANTωNINOCCEBE/VC
R: Serapis std l inside a temple, TPICKAIIς

The Greek "16" after the date is supposed to have recorded the number of Cubits the Nile rose that year, 16 cubits being 7.315 meters or 24 feet which appears to be about average for lower Egypt.  

Ex: CNG 418 (11 April 2018) portion of lot 662