Video from Leica on lens manufacture.
I have to say the only lens I've ever had that fell apart on me was made by Leica! The aperture ring on a 90mm f/2.5 Summarit-M I had became disengaged. They did repair it free of charge, but even so.
I should have listened to Ken Rockwell - http://www.kenrockwell.com/leica/90mm-f25.htm
This is an old video from Digital Rev on using Leica lenses on m4/3 cameras.
Finally the Ricoh GXR Leica M lens module.
