Originally posted by Lord Lucan I have this lens. I bought it used with a K mount.
Years later I realised that the basic lens barrel ended at the back end in a cylindrical stub with a groove around it. A K mount adaptor was fixed to this by means of three recessed radial pinch screws 120 degrees apart. I have just taken mine apart for this photo, for which a jewellers screwdriver is needed. You can see one of the screw recesses at the top of the adaptor. The inner ends of the screws pinch into the groove to make a firm attachment, and in my photo you can see a tiny bright witness mark that a screw has made.
I don't know anything about the Adaptall or T-mount systems - is this it?
What your picture appears to show is a partially disassembled T2 mount. On "most" T2-mount lenses the "v-groove" part, where the screws locate, unscrews from the lens itself, that is to say it's part of the mount, not part of the lens. If this is the case it's simply a case of screwing on a different T2 mount to suit the new camera. The three screws are there simple to allow the lens body to be rotated with respect to the mount so everything lines up nicely when it's mounted on a camera.
Unfortunately not all T2-type lenses follow the rule, making the "v-groove" actually part of the lens … it's cheaper to machine a groove than a fine thread! This is unfortunate, because, although T2 mounts in their entirety are interchangeable, the component parts of the mount may vary between manufacturer. For example, the "v-groove" part may be slightly bigger (or smaller) from one manufacturer to the next.
Not a problem if you've got a lens which needs a complete mount, but some mount "outers", the part with the camera bayonet on, may not fit a fixed "v-groove", necessitating trying several different mounts to hopefully find one that matches the lens (bin there, done that!)
Good luck