I picked up a job lot of filters and hoods, which included an Itorex 50mm f40 (and yes, I meant 40, not 4.0) lens. It's basically a very simple pancake lens which is about f2.8 and fits into a T-mount, with a removable disc that fits between the elements to stop it down. The disc was missing but I cut one from the black vinyl wallet an old multimeter came in, with the diaphragm burned through as a pin hole. Doesn't focus, but doesn't need to because the tiny aperture gives huge depth of field (but of course means exposures are VERY slow), but even stopped down it isn't incredibly sharp. Here's a quick test with and without the stop disk:
Unfortunately the T-mount it came with is the old Contax-Yashica fitting, which is fairly useless, but I had a spare Nikon mount to try it.
I don't think I'll be keeping it, but it was fun to play with.