The back says "Convert us, O God: and shew us thy face, and we shall be saved" from Psalm 79.
The front mentions Leo XIII, Sainte Face, and Tours 1885. Still looking...
Looks like the cross of the Archconfraternity
of the Holy Face
, established by Leo XIII in 1885.This ancient and venerable Catholic practice is rooted in the representation of the face of Christ said to have been left on the towel or veil used by a holy woman thought to be named, Veronica. An Archconfraternity of the Holy Face was established in Tours, France, 1884; its members make reparation for the blasphemies hurled at Christ. Since St. Therese's devotion to the Holy Face has become known, this devotion has spread worldwide.The Holy Face