Magnentius - CHRISTOGRAM!

Magnentius, 18 January 350 - 10 August 353 A.D.
This reverse was meant to incite the Orthodox Christians of the West against the Arian Constantius II, who intended to reclaim the western provinces. -- Coinage and History of the Roman Empire by David L. Vagi
A1179. Bronze centenionalis, RIC VIII 320, Trier mint, 5,9 g, 25 mm, 352 A.D.; obverse N MAGNENTIVS P F AVG, bare-headed, draped and cuirassed bust right; reverse SALVS DD NN AVG ET CAES, large Christogram (chi-rho), flanked by alpha and omega