Constantine II, AR one-third Siliqua, 12mm, 0.72g. ca. 330 AD. Constantinople. 

no legend, pearl-diademed, draped, youthful bust right. 
Large K, no mintmark or legend.

RIC -; Cohen 287. 

Very rare.

Contributed by Dr. Hubert Lanz, auction November 2000, 
Added July 2011.