I have never noticed them before. 87 and still learning! Thanks, old friend! And remarkable photo and coin!
Heres two Probus with left (Siscia) and right (Rome) facing busts, both ADVENTVS.PROBI.AVG. Both mark the arrival of Probus in Rome, 277 CE.
Killer captures @ominus1 ! Scotty would be PROUD! PROBI RI Probus 276-282 CE Ant 21mm Rome mint captive on ground Riding Horse in ex R-Thunderbolt-Z RIC 155 RI Probus 276-282 CE BI Ant 2.80g Cohen 768
@Jims Coins: I took the liberty to put your obverse and reverse together in one image. It makes it easier to view. Nice coin btw.