Constantius II, AR Siliqua. 340-351. Constantinople. 2.76 gr. 

DN CONSTA-NTIVS AVG, rosette-diademed, draped, cuirassed bust right.
FELICITAS REIPVBLICE around VOT XV MVLT XX within wreath.

Mintmark C dot Z. 

Lanz 102, 1026; RIC VIII Constantinople 58 var (unlisted officina); RSC 68a.
Very rare.

With permission of Numismatik Lanz, auction 102.
Lanz 102, 1026.