Angenieux zoom lens · unknown mount

Hello,

I bought a Bell & howell 16 mm camera (la GB-Bell + Howell 603T Autoload de 1955, according to google). It has an Angénieux zoom ( type L1, F 17-68 mm) with a mounting system that need to be turn to be locked. But I have search and search. I cannot find any info on that particular mount. So I am turning over you because I'll like to know the name of the mount system or if anyone has ever see such ring system. My crazy hope is to adapt a c-mount to the zoom to be able to use it on my GF1.

The mount on the camera

the ring on the zoom

The zoom locked on the camera. You have to turn the ring to lock the lens on the camera

An info I found on the net. According to the drawing, the adapter (c-mount) is not supposed to be fixed on the camera. But it looks like it is on mine despite all the tries I did to unlock it from the camera.