This celluloid knob is quite small, only 1/2 inch round. We envision it being used on a lid of a small box. The celluloid stem probably is not real useful; the knob may have originally been screwed into a paperboard box. The knob could now be secured into wood with glue.
The ball-shaped knob and its stem project from the surface 3/4 inch.
This is truly an interesting knob.