A bit of gentle googling this morning found that the RO brevet was introduced by AMO A402/41,the wearers designated as Observer Radio.
The wearers were redesignated as Navigator Radio by AMO A1019/42.
But of course the Radio designation which may have caused a little confusion was merely an attempt to confuse the nastys as to the real purpose of this category of aircrew.
I had forgotten that the RO badge was reintroduced post war,as another poster asked,was it the same badge??presumably their designation would have been ‘Radar Operator’