I've seen this and similar Leica manufacturing videos before. The thing that strikes me is the visible dust on the optics during manufacture, and the lack of gloves or finger coverlettes, and lack of face mask and hair net, by many of those assembling lenses and cameras. Conversely, I've seen videos of lens manufacture in Japan, and there it seems adherence to some sort of cleanroom protocol is more strict.
Interesting video, thanks for posting.
~Joe