<<At the base of the distributor was an an adjustment for octane. You could move the distributor until the pointer was at the octane you were using at the time. >>
I have a 190SL that has a knob on the dash that turns the dist from in the cabin.
The manual says to go up a 15 degree grade in top gear and adjust back from 'Pinking" !!!!
PINKING - gotta Love it,,,