Just PROBUS? Or why you say marcus Aurelius? I found now PROBUS RIC 753 Probus AE Antoninianus. Siscia mint, 281 AD. IMP C PROBVS P F AVG, radiate cuirassed bust right / SALVS AVG, Salus seated left, feeding snake rising from altar from a patera, XXIVI in ex. Cohen 591
Ok ... I think I found on wikipedia. Probus just have same name like marcus aurelius Marcus Aurelius Probus Augustus. http://en.wikipedia.org/wiki/Marcus_Aurelius_Probus
A antonianus of emperor Probus 276-282 ad, it is not made of silver, its a 96 percent bronze, 4 percent silver coin, with a silver wash. Worth maybe around 10 to 15 dollars