We have White Porcelain Door Knobs with Ornate door plates Vintage items.  The center bar is square and they measure about 5 7/8" from one side of the door knob to the opposing side.  The knobs are about 2 1/4" across the face of the knob x about 2 1/8" in D.  The metal building up to the porcelain on the knobs is metal and completly rusted.  There are 2 door plates, round on the bar in the center.  They are ornate in design - they do have some rust on them as well. 

Door Knobs White Porcelain with Ornate door plates Vintage