So, I found another unusual photographic item in an antique shop: a Mamiya-Sekor Macro E 50mm f/3.5 lens with a matching extension tube. For $20 I couldn't pass it up. This is a late-model lens for a Mamiya 35mm SLR, probably from the early 1980s. Some internet searching has turned up a little information, and it appears that the previous mount (Mamiya CS) version of this lens is rather rare. A couple things I have noticed playing with it. 1) The lens aperture is normally at the minimum, f/22; apparently these lenses were at least partially electronically-controlled. Pressing the mechanical aperture lever opens the lens up (seems like this would make it difficult to adapt to a Nikon SLR, even for bellows use; I think I might be able to attach it to a Nikon E2 tube and use the plunger to manually adjust the aperture). 2) It appears to cover 6x7! If I place the lens flush against the throat of my RB67 I get a full screen image. Of course there's no shutter but I could use it for flash or very long exposures. Anybody have thoughts on this item? Is it worth looking up a Mamiya ZE-X or similar body just for this lens?