Notch on lens mount

[Symeon]

Does anyone know why some Leica lenses have this notch in the mount?

 

[nikon_sam]

My guess its a lens lock...does it line up with anything inside the camera...I've only held a Leica once in my life...so not an expert...

 

[Phil_F_NM]

Not THE lens lock, that cut is at the wide part of the flange base, not the ears.
I've wondered about this cut myself and I feel it's probably a remnant of assembly line process or there to allow mounting the lens for collimation without having to engage the lock which the M camera uses. Use of this in testing a lens could produce a marking which would render the lens used right from the factory floor. Those are my ideas, but I'm curious to know the answer.

Phil Forrest

 

[Beemermark]

My guess it is a locator for when they machine the mount.

 

[oldwino]

It is a vestigial tail.

 

[Rayt]

You’ll find the notch on early M lenses. It couples with a place holder for precision machining.

 

[Rayt]

My guess it is a locator for when they machine the mount.

This......