In my experience, The Nikkor-HC is a faithful reincarnation of the Carl Zeiss Jena 5cm f2 Sonnar "T"- except in the proper focal length for a Leica and available in LTM. I remounted a wartime CZJ 5cm f2 Sonnar "T" in LTM, and have used both with film and with the M8. The coating on the Nikkor is harder and less prone to damage than the Zeiss, especially the inner surfaces. The threads used for the retaining ring of the Nikkor is the same as that used on the Zeiss optics module, also the same as the I-61. If I decide to remount the latest CZJ 5cm f2 Sonnar "T" in LTM, it will be with a Nikkor mount. Right now, it is shimmed for S-Mount and on the Nikon SP. I do not have a Collapsible S-Mount lens, my collapsible Nikkor is in Leica mount.