Yes the fan switch knob has the flat spot on it too, set at between 9 and 12 / when off
The little clear plastic centre is visible through the small hole but is not flush with the outside of the knob it is recessed a little.
With the knob off, the clear plastic protrudes about 6-8mm from the brass of the switch body.
Graphics' description of the bulb location is accurate for my car too.
One point about the knob.... There is a small wire type C clip around it that holds the knob onto the chrome collar that screws onto the switch body that protrudes through the dash .
My fan switch always squeaks, this might need to be lightly greased.
I don't intend taking it out to photograph it at this stage.
Bob (Brisbane,Australia)
RHD,1967 early 250 SL, auto