Tacitus AE Antoninianus. Serdica.

Obv: IMP C TACITVS INVICTVS AVG, radiate, draped, cuirassed bust right.
Rev: PROVIDEN DEOR, Providentia, holding two standards, standing right, 
facing Sol, holding globe, and raising right hand, standing left. 
Mintmark KA delta.

RIC V (1) 197, rated scarce.
Courtesy of Dirty Old Coins.