Here's an extremely rare little lens you've read about but never seen.
I think they cover about 100 degrees. Teeny tiny. Like a Zeiss Protar V
13CM was intended for the 6.5X8.5 Full Plate crowd, but I've pressed it into service on 8X10. It covers, barely, and to be honest, the corners were not acceptable. Best to confine it to 6½X8½ like it's supposed to be used.
It's in wonderful shape with a bit of dust inside and perhaps some paint loss. Aperture is perfectly round and works great. Nice sharp little lens, and the Vade Mecum says it's one that should prove excellent in use, even by today's standards. $265