Bill, that Variogon is a larger mount than a C. I have a couple of C mount lenses, and the S-K is not similar. It is almost 45mm across, with a four hole flange on the screw portion of the barrel, and a large baffle on the rear. That could be milled down, but still would project into the mirror box a bit. Another feature is the lens is self erecting, and has a mask inside. I'll have to do some research to see what it was used on.
PF