This painted knob is quite old. It is possible that the paint is original. Why do we know it is old? 1) the stamped brass face of the knob is crimped onto a steel base piece; 2) the knob has a wood neck or spacer. We usually only see these on pre-1900 knobs; and 3) the bolt is embedded into the knob’s base and has an old nut.
The knob measures 1 1/4 inches in diameter. The base of the wood neck is 3/4 inch round. The knob projects from the surface 1 1/8 inches.