Repairing a Schneider-Kreuznach Retina Xenon 50mm f/1.9 Lens

Recently, I got my hands on these three Schneider-Kreuznach Retina-Xenon 50mm f/1.9 lenses. These were manufactured between 1959 and 1971 and they all feature the DKL mount, for Kodak Retina rangefinder and SLR cameras. These are fundamentally the same lens, however with smaller variations.

Two of them (left and right) have a cam for rangefinder cameras and a minimum focus distance of 0.9m (the left one has a distance scale in feet, and the right one in feet and meters). The middle one does not have a rangefinder cam, but a minimum focus distance of 0.6m.

The left one has the rangefinder cam - the right one does not.

All three had a pretty stiff focus, so I cleaned them. 

More of my lens repair tutorials can be found here.