Focusing mount for 90 summicron?

I've got a 90 summicron that has the visoflex short mount on it, which obviously will not mount directly on a camera. What am I looking for i.e. the Leica abbreviation, for a focusing mount that will allow the lens to mount directly on an M camera?

I looked at E bay and I see a few of the short mounts, bit nothing in a longer mount.

Donno the product code I'm away from documentation but the rfdr mount was commercialised separately as late as circa '74, you sent the lens back to factory I think, as the mount is matched to the lens, i.e. the lens focal length code and the mount focal length code are/need to be identical pairs and there may be hand building as well perhaps.

The viso and rfdr mounts were not the same between different versons of the cron, the 'wrong' viseo mount will not have the correct infinity stop, scale.

Sorry

Noel

Somewhat by coincidence, right after I posted the original question, I found a "parts" lens on E bay. The elements have fungus, but I don't care as I'm not using the glass, just the mount. It's on it's way to me now.