When it comes to off-brand interchangeable lenses for rangefinder cameras, nothing can match the sheer number and staggering diversity of rangefinder-coupled lenses available in Leica screw (LTM) mount. Perhaps this shouldn’t be all that surprising since the classic “Barnack” rangefinder Leica was in production from 1932 (the first Leica II, Model D) until the last Leica IIIg was phased out in 1960. Yes, you can occasionally run across non-Nikon lenses in Nikon S mount and non-Zeiss lenses in Zeiss Contax rangefinder mount, but they are few and far between compared to independently made Leica screw mount lenses.
Of course, virtually all Leica screw mount lenses (with a few early and special purpose exceptions) are mutually interchangeable with those made for Canon screw-mount rangefinder cameras because Canon then used the same mount, flange focal distance, and basic rangefinder coupling system as the screw-mount Leica. And of course, during the ‘50s Nikon offered a series of outstanding Nikkor lenses in Leica screw mount ranging from the 25mm f/4 W-Nikkor C to the 135mm f/3.5 Nikkor-Q, including such standouts as the 50mm f/1.4 Nikkor-S C, the 105mm f/2.5 Nikkor-P C, and the unique 50mm f/3.5 Micro-Nikkor.
To give you a better idea of the ingenuity that other leading optical companies, and a coterie of talented machinists, put into designing and adapting lenses to work on the legendary screw-mount Leicas, here are 5 fascinating examples, 4 from Germany and one from the good ol’ U.S.A.