This knob appears to be solid brass, but considering its age and era, it may be cast bronze. Manufacturers of the late 1800s, often preferred the bronze medium.
It’s diameter measures 1 1/8 inches. Once installed it will protrude out from the piece about 7/8 inch. The base is 5/8 inch wide. The stem (screw on the back) is about 5/8 inch long and is iron.
Being solid brass, these knobs are heavy, giving a real sense of quality workmanship.