Augustus Prouty received a patent # 224,040 on February 8, 1880 for the latch and #235,963 on December 28, 1880 for the lock used with his knobs. The knob pictured is an inside knob as indicated by the "O"on the button. The button is unscrewed to remove the knob. The exterior knob had a different design,K-12500.SeeAntique Builders' Hardwarepage 179.  The interior knob is composted of four parts. The inside iron is screwed to the exterior knob.  It is covered with the rose, the knob sits on the end of the iron and is held in place by the button piece.