Other than a few special models like high speed cameras, dentistry kits, things made for microscopes, industry/military/NASA cameras with special mods, Olive Drab bodies, one version of the F-1N that I've seen with registration pins for very precise multiple exposures, and Olympic logo bodies, there are three common versions--the F-1, F-1n, and New F-1 (commonly called the F-1N, but not in any official Canon literature that I've seen). You might come across one of the rarities occasionally, but I wouldn't make any plans about acquiring one.