From elsewhere:
At the end of WWII the military air VHF band was 100-156MHz. Transmit frequencies were derived from crystal oscillators working in the range of 5.560MHz to 8.665MHz which were electronically multiplied by 18 to give the transmitter output freq.
The oscillator crystals were manufactured at 5KHz spacing, which when multiplied by 18 gave an output channel spacing of 90KHz. Thus there were some 622 channels available from 100.08MHz to 155.97MHz at the end of WWII.
When civilian aviation started they were allocated 108-128MHz initially (100KHz channel spacing). 108-118MHz was allocated to navaids and 118-128MHz to R/T. The old RAF common freq of 117.9 was so widely used, that it must have been kept clear of navaid use until the RAF finally gave it up. Many civil aircraft also carried 117.9 (it was only a matter of plugging the appropriate crystal in).
As late as 1973, our ULAS Chipmunks still had ancient 10-ch VHF sets, complete with utterly useless obsolete VHF frequencies. No doubt there was some aged Learning Command edict, which no-one had reviewed, stipulating that 'RAF Common' and 'NATO Common' frequencies were to be carried?
When the RAF woke up to extension of the aeronautical VHF band from 136 to 137 MHz, the only way this could be achieved on some of our VC10K V/UHF radios was by sawing off some internal mechanical part, to enable the VCO to go up that high. But this also had the effect of lowering the bottom available frequencies by 1 MHz...
, which would have caused interference to some navaids.
The only RAF aircraft I flew which had the full range VHF band (up to 150-ish MHz, I think) was the Hawk T1. Tootling back along a TACAN route from Scotland back to Chivenor once using UHF, I clicked through the VHF radio's channels to see what was there as the coverage included various 2m frequencies used by taxis and other mobile users - as I soon discovered!