Aemilian AR antoninianus. 

IMP CAES AEMILIANVS PF AVG, radiate, draped and cuirassed bust right.
PACI AVG, Pax standing left, legs crossed, leaning on 
column, holding branch and transverse sceptre.

RIC 19; RSC 26a; Sear -.

(Image taken from the RIC volume).
Extremely rare. Only one example known to RIC author (British Museum).