Constantine II as Augustus, AR siliqua, 21mm, 2.91 g. 

No legend, laurel and rosette-diademed head right.
CONSTAN-TINVS AVG, Victory walking left, holding wreath and palm branch. 
Mintmark SMK. 

RSC 69Af; RIC 1 var (mintmark)

With permission of Numismatik Lanz München, Auction 114, Lot 825, May 2003.