The knobs themselves are approximately 1.25" diameter, with a 1.75" diameter base plate, and protrude approximately 1.75".  The screws are a bit over 2" and approximately 1/8" diameter.  The knob and base plate are two pieces.  Please note the brass finish on the knobs has some wear from age and use - some spots, scuffs, scratches, marks, etc, please see photos 7 and 8 for close up examples and for details.