Presumably, you wish to use the chuck on a machine which does not have a camlock facility? Otherwise, why bother?
By the looks of your picture, there are still two parts there, (visible in the centre and below the body proper) the body, which carries the three pinions, and a backplate.
Are there any tappings into blind holes? If YES, then setscrews (jacking screws) can be screwed in, and progressively tightened to push the backplate off the body. If there are no such tappings, you should be able to produce three, for the task.
Howard