NOS genuine Mercedes vent window knob- 1117605266 and cap- 1117600567 for models of the 60’s.
Be sure you are getting the correct cap because the chrome ring is thicker than later version which is shown on the right in the photo. You are getting the cap on the left.

The diameter of the knurled knob is 2 inches. The metal shaft is also shorter at 1/2 inch than the later version. The thickness of the knurled edge is 1/2 inch.  I also have just the caps in clean condition. Ask for details.

I point this out again to be sure of what you want, because I also have larger knobs which are 2.25 inch diameter and with a wider edge and longer shaft.