Semasia was a localized personification that may best be described as "Alexandria riding on horseback." She wears the elephant cap of Alexandria, and appears astride a galloping horse. Her type is found only during two years of Marcus Aurelius's reign, if one wishes to except the semi-medallic drachmas of Philip's tenth Alexandrian year. All coins showing the type of Semasia are scarce.
Curtis,The Coinage of Roman Egypt: A Survey
Milne 2538 Marcus Aurelius
Curtis (1990) p. 303 coin 343