Hi David / Bob,
You are quite right David, it wasnt a watch makers lathe, Bob is correct, it was done on a big 10″ Emco. 
I did wonder though if it might be simpler to fabricate something like this as opposed to a steady rest? The one my friend Daryn has is not a radius tool, it is just a guide for cutting and supporting, his is quite a lot smaller than the thing pictured, I am pretty sure his does not have a bearing, he just cuts a brass “bush” to match the size of the holder and the inside diameter to the size of the work. The cutting tool is then set to cut to the required diameter. A great method for turning new arbors with the pinion blank.
Paul.
