For your consideration, here is a Vintage Rusty Rustic White Porcelain Door Knob.  It has a diameter of 2 1/8 inches and is 1 ¾ inches deep.  It is missing the holding screw.  It is worn and the metal has a rusty surface.  There is a chip in the porcelain 1/8 inch in diameter. 

It will be mailed in a box for protection.  Item pictured is the actual item up for sale and comes from a non-smoking household. (639.9a88b-.9bx2)