I have just bought a lathe with a Reishauer RH250 chuck on it. It is a 10 inch 3 jaw chuck. It has one pinion to drive the jaws; this is tangential to the spindle axis, not radial as on a normal 3 jaw. There is a pin that seems to be a ratchet to release the jaws, and they can be mounted at differing distances from the centre of the chuck, so you could mount an offset piece rather like a 4 jaw independent chuck. The jaws are reversable.
Any background or help on using the chuck would be appreciated.