This is an oversized knob! Perhaps this one was made for a front door. The standard size of most door knobs is 2 1/4 inches, but this beauty measures 2 5/8 inches across. The knob has a high dome and is belted. The pattern continues on the backside. This brass (or cast bronze) knob was made by Russell & Erin Manufacturing Company of New Britain, Conn. around 1885.
This cast knob has the damascene pattern. It extends 2 1/2 inches from the surface. The neck measures OD 11/16 inch across. The knob accepts the standard size spindle.
This is a fine old, old knob.