Siglos was the Greek transliteration of the Semitic denomination "shekel" which became a standard weight unit for silver in the Achaemenid Persian Empire after the conquest of Babylonia by Cyrus the Great in 539 B.C. Ironically, silver sigloi seem to have been struck primarily in the western part of the empire and the standard went on to influence several Greek civic and royal coinages in the fifth and fourth centuries B.C. There is endless debate about whether the figure on the obverse represents the Persian Great King or an anonymous royal hero, but since the Greeks regularly referred to the parallel gold denomination as the "daric" it seems clear that at least some contemporaries considered it a depiction of the king. Of course, whether this is what the Persian authorities intended or an example of interpretatio Graeca must remain an open question.