Severus Alexander, AR denarius, engraver's error. AD 228-231.

IMP SEV ALEXAND AVG, laureate head right.
ANNONA AVG, Annona standing right, foot on prow, holding 
sceptre and modius.

RIC 190 var (sceptre); RSC 32a var (ditto).
Probably an engraver's error, left as it was when the
engraver omitted to engrave the base of the rudder which
Annona is usually holding. 

Contributed by carpe diem nvmismatics, Dec 2014.