Leicaflex

Leicaflex began with the introduction of their SL camera in 1964, four years after Nikon F had been in the market. It was a robust camera but very expensive to build. Leica engineers built it like their rangefinder cameras (mirror housing dropped from top). This was a disaster to implement, and the Japanese way of making cameras (installing the mirror box from front) became the standard for 35 mm SLR design. At least they didn't fall in the trap Bronica fell into, for many years designing cameras with vierd mirror mechanisms to allow lenses sit deep into the camera to allow a better lens design. Prior to release of Leicaflex, Leica fans used Visoflex (below, right) that attached in front of their M body, and had to use special lenses for the added distance. In fact Leica M1 was specifically designed with no rangefinder for Visoflex reflex viewing.

Visoflex with detachable viewfinder