Lens mount for 70mm Russian camera....what is this called?

[Henri Titchen]

Hi,

 

I came across a lens recently that has a mount as shown in the drawing attached. Can anyone identify this mount?

 

The lens is for a Russian 70mm motion picture camera. (The russian cameras used 70mm not 65mm).

 

The model of lens is OKC4-75-1 (Focal length=75mm).

 

Thanks,

H.