Probus AE Antoninianus.

Obv: IMP CM AVR PROBVS AVG, Radiate, helmeted, cuirassed 
bust left holding spear and shield
Rev: SOLI INVICTO, Sol in spread quadriga, holding whip

Mintmark KA dot delta below horse's legs

RIC V-2 Serdica 862, rated common

Dane's collection, January 2010