[Graham Boak]

You originally posted "many units" - I believe it to be few, and you will have difficulty coming up with more than a handful of examples. After all, orders were to be obeyed, not to be argued over or got around to when convenient.

You seem to be looking for specific orders to those lagging units, which I rather doubt you will find. More likely it will have been a "word of mouth" comment between fellow officers - "Good Lord, you aren't still using those prewar codes!"

As for parallel use, surely this would only have been very temporary, and only a matter of working through the unit's aircraft with a few pots of paint. Days at most.