Alexander of Carthage, AE follis, 21mm, 5.56 g. AD 308-311. 

IMP ALEXANDER PF AVG, laureate head right.
GLORIA EX-ERCIT KART, Emperor, radiate, on horseback riding 
right, right hand raised.
Mintmark PK. 

RIC VI Carthage 65; Sear 15082.

Very rare, rated R4.

With permission of Numismatica Ars Classica, auction 88, Lot 496, Oct. 2015.