Watch List notes:

Probus. A.D. 276-282. AE antoninianus. Siscia mint. IMP C M AVR PROBVS AVG, radiate bust left, wearing imperial mantle, holding eagle tipped scepter / ADVENTVS AVG, Emperor on horseback, Δ between horses legs, XXI in exergue. RIC 624. VF. 

Ex Blackmoor Hoard.