Probus Antoninianus, 3.70g; 24mm, 277-282 AD. Siscia. 

Obv: IMP CM AVR PROBVS P AVG, radiate bust left wearing imperial 
mantle, holding eagle.tipped sceptre
Rev: VIRTVS PROBI AVG, Mars, heroically nude, walking right, holding spear and trophy

VI in lower right field, mintmark XXI. 

RIC 812 var (obv. legend); Alföldi 96.127. 
Scarce.

With permission of Roma Numismatics, December, 2009