Zeiss Tessar 50mm f2,8 disassembly and cleaning

Carl Zeiss Jena camera objective Tessar 50mm f2,8 disassembly and cleaning.
Some notes:
1. Parts of the aperture mechanism were missing. It's not something I could fix but it's still usable. Maybe it's the result of some crude repair or it was intentionally declicked, idk, but looking at the screws you can tell it has already been taken apart by someone.
2. The foucusnig mechanism on this lens looks as if it was designed to be hard to get apart. You just can't do it without having to reset infinity afterwards. For this reason I don't recommend screwing with it if you have no experience.