Probus, AE antoninianus. Siscia mint. AD 276-282. 

IMP CM AVR PROBVS PF AVG, radiate, cuirassed bust right, holding dagger (pugio).
CLEMENTIA TEMP, Emperor standing right, holding sceptre and 
receiving globe from Jupiter, standing left, holding 
sceptre. 

Digamma in lower centre. 
Mintmark XXI. 

RIC V-2 643 var (bust type). 
Very rare.

Courtesy of the Philippe Gysen collection.