Probus, AE antoninianus, Siscia. 21 mm, 3.67 g. 

IMP PROBVS P F AVG, radiate, cuirassed bust right.
PAX AVGVSTI, Pax standing left, holding olive branch and transverse sceptre. 

S in right field. Mintmark XXI. 

RIC 713.

With permission of Auctiones GmbH eAuction 7, Lot 102, June 2012.