You got me there. I have been dismantling the GX dash & I have removed the light & wiper switches as well as the double choke cable & cigarette lighter. The brown that you can see in the picture is just plain filth.
I took to the knobs with a little cleaner & warm water & they are now blacker & brighter.

I also have a PB110 Excellent parts book, so I looked it up.
The knobs normally come with the switch [or whatever] & look the same as regular 1200 knobs in the illustration, however there are more options than I thought.

I looked at the light switch for example & here's what I found. To simplify things,I will substitute a letter for the part number.
DX= Deluxe. GL= Grande Luxe. GX= Goes Xeptionally well

Switch A. lighting for DX & GL
Switch B. Lighting & fog lamp GX [opt GL & DX]
Switch C. Lighting & fog lamp with illumination [opt all]

Knob A. Lighting switch [all]
Knob B. Lighting switch with illumination [opt all]

Switch 'C' iluminates the center part of the knob when it is on but this optional switch seems not to have been fitted to this particular GX dash.

The shaft in this lighting switch is siezed, so I will need to free it up in order to determine if it is the correct lighting & fog light switch which is shown as standard for GX.

There are four washer switches. Up to 12/71 with & without illumination, then 'from 1/72', with & without.
Four knobs for these switches too, but no reference to a brown rim.

I checked my 1200 parts book too, & for Australia, we use a different lighting switch 'D.' but the same old 'Knob A.'