Tacitus AE silvered Antoninianus. Rome.

IMP CM CL TACITVS AVG, radiate head right with slight drapery on
left shoulder.
CLEMENTIA TEMP, Clementia standing left, leaning on column, legs 
crossed, holding olive branch and sceptre.

Z in right field.
Mintmark XXI.

Estiot 1115, La Venera hoard 1679, RIC 84 var (field mark, bust type)

Courtesy of Athina Numismatics, Dec. 2009.