I have written about a dismembered Missal of Leo X several times, most recently here. Browsing images of cuttings in Parisian collections I came across this initial "P", in the Musée des arts décoratifs, shown above.
The online description is vague:
Unlike those previously found, the cutting consists not just of an initial, but also a border:
This is also the first cutting to show any evidence of music (a four-line red stave is visible to the right of the initial "P", with a musical note on the top line). I suspect it comes from the Prefaces which usually precede the Canon in missals, and begin "Per omnia ..." as in this example, which also has a priest doing something with the chalice:
-- two cuttings at Vassar College
-- one in the Wildenstein Collection, Paris
-- one sold by Maggs c.1970
-- one sold by Christie's in 2016
-- the present one, in Paris
Doubtless more will come to light ...