375-350 BC, as stated by Dubois
around or before 500 BC
ca. 500 BC (dated on letters form)
issued in the seventh year of the kingdom of Ptolemy (i.e. Ptolemy III) son of Ptolemy (II) and Arsinoe (240 BC), on the second day of the month Dystros (February: Dittenberger et alii; May-June: Sherk), under the priesthood of Theodotos