Regalianus. Billon antoninianus, Carnuntum mint, AD 260. 

Obv: IMP C P C REGALIANVS AVG, radiate and draped bust right
Rev: ORIENS AVGG, Sol, radiate standing left, cloak falling 
from shoulders, his right hand raised holding whip

Overstruck on a denarius of the Severan period.

Göbl (Regalianus und Dryantilla) M1 and Plate II, RIC V 7, RSC 4a, New Sear 10844. 

extremely rare (R5)

With permission of Dane's bank, UBS Numismatics, Sept. 2008
(New Sear reference added in 2016)