Constantius II AR Siliqua. Trier. 342-343 & 347 AD. 

Obv: FL IVL CONSTAN-TIVS PF AVG, rosette-diademed, 
draped & cuirassed bust right
Rev: PAX AV-GVSTORVM, Emperor standing left in military dress, holding standard with chi-rho on banner, TRP 
in ex. 

RIC VIII Trier 170, rated R3 (very rare)

Found in England in Autumn 2008 by John Brien, registered
with PAS.
Added July 2009