Marconi 2019 second degree protection code?

I'm repairing a Marconi 2019 Signal Generator and I want
to re-calibrate the thing. For this I need the code to
overcome the "second degree protection" (top-secret in
this apparatus. Does anyone know this key-sequence?

 

Quoting from the technical manual:

"Press SECOND FUNCT, 0, then in the rotation given first MOD OSC
then ON/OFF and finally CARRIER FREQ keys holding down all three
keys for a minimum of 5 seconds.
Follow this by pressing SECOND FUNCT and the numeral 7, 8, 9 or '.'
as required."