Tacitus AE Antoninianus. Siscia Mint. 

IMP C M CL TACITVS AVG, Radiate,
cuirassed bust r. / 

PAX AVGVSTI, Pax advancing l. holding branch and
sceptre; VI in exe..

References RIC unlisted. Cohen unlisted. Estiot, Venera Hoard 2365, one
specimen listed, plate 19, different dies than this example, Siscia, not 
in RIC though it was described in the original hoard published 
in 1880. 
One specimen in Venera Hoard and the absence of this variant 
from Cohen must mean it's at least a very scarce coin.

Contributed by Martin Griffiths, April, 2004.