A nice, fully legible example of this issue.
Obverse: a bust of the emperor, wearing a radiate crown and consular toga, holding a scipio, facing left; the legend on the rim reads:
IMP C PROBVS P F AVG;
Reverse: Pax standing facing left, holding an olive branch and a long scepter; the legend around the edge reads:
PAX AVG, with a “P” in the right field, in series XXI;
