Knob attachment based on patent # 255,858 by O.M. Hidden, April 4, 1882. Likely made by Union Doorknob Co. Detroit, MI See TDC # 180Knob diameter is 2 1/2  inches. The spindle goes through the outer knob. The other end of the spindle is grooved. The outer knob and spindle inserted and the pincher is pushed against the rose. The enter knob put on and pulled tight by the screw.