Calhoun Rapid Convertible 17x22 lens

I recently brought a Calhoun Rapid Convertible 17x22 lens to use on my
11x14 Seneca view camera. It a large brass lens. Although I haven't
exposed any film with it, I've mounted it in a lensboard and tried it
on the camera. Needless to say, I haven't been able to find the limits
of it's coverage with my 11x14. It seems to be about a 640mm. It seems
quite sharp, certainly good enough for contact prints. I've tried to
research the lens, and haven't been able to find anything. Does anyone
know anything about it?

Never heard of it. You may be able to get some clue as to its
construction by counting relflections. Shine a small light into it, a
pencil flash light is good. Bright reflections are glass-air, dim ones
are cemented. I suspect its a Rapid-Rectilinear clone but it might be
something else. A R-R will have two bright and one dim reflection in
each half.

Richard Knoppow
Los Angeles, CA, USA