As early as 1952, two young engineers: Karl Cloes and Paul Naumann began the first Leica SLR reflex camera research and development, and he was listed on a patent filed in 1961 with Werner Schlapp.
Source - 
E. Leitz Photographic Patents by Paul Naumann
- 1961 MAR 02 - REFLEX CAMERA with Werner Schlapp (see above)
- 1961 DEC 26 - MONOCULAR REFLEX CAMERA with Ludwig Leitz (see Leicaflex Mark 1 and Mark 2}
- 1966 MAY 25 - DRIVE DEVICE FOR CAMERAS (while living in Alkmaar, N. Holland)
- 1966 JUL 05 - FOCAL-PLANE SHUTTER (while living in Alkmaar, N. Holland)