Found something else (which you've probably already seen, of course). The 1938 Tele-Xenar leaflet at this link lists a Xenar 7 1/16" (18 cm) f/3.5 lens capable of covering 5x7.
There's also a reference to a 180mm f/3.5 Prolux projection lens, but I found no information on the optical formula - it's just an entry on the Wiki page for Schneider.
And then, there is the entry on this table for a 7 1/8" f/3.5 Schneider Xenar. The source is given as the Burke & James 70th Annual Catalog, published in 1967. So apparently Schneider did make such a lens at some point.