Probus, AE silvered antoninianus, 280-281 AD, Serdica. 3.41 g. 

IMP CM AVR PROBVS P AVG, radiate bust right, wearing imperial
mantle, holding eagle-tipped sceptre.
SOLI INVICTO, Sol in spread quadriga facing, holding whip and
raising right hand.
Mintmark KA dot gamma.

RIC V-2 Serdica 862 var (obv legend, bust type)
Rare
Helios auction 5, lot 422

With permission of Helios Auction 5, June 2010, lot 422 
Added in Aug. 2011.