Hmmm. Yeah, I'm kind of puzzled by it too. I can't figure out why you'd want a 40mm lens instead of a 50mm one. Here's the exact markings on the front:
Schneider-Kreuznach 14048073 Componon 1:4/40
Aperture ring has detents for 4, 5.6, 8, 11, 16. And of course, says "Lens made in Germany" on the side.
Thanks for all the suggestions so far. Doesn't really seem like something I need, I guess, but maybe I'll try it out and see what the results are just for kicks?