RAF Civilian Wireless Reserve

[SAS1]

In 1938 the RAF CWR was set up which recruited amateur wireless Hams around the country, which were then mobilised after the start of the war, sometimes within days, travelling to France to operate wireless receiving stations.

They were issued before the war, with a lapel badge of a shield surmounted by an eagle, and this is described in 'Flight' Magazine of November 1938. However, at some point a second version appeared with the addition of a letter 'C' on top of the eagle. Looking at the two badges it seems the 'C' might have been added to the original die as there seems to be a distinct line as if it was added later.

Does anyone know what the 'C' represents? The only thing I can think of is 'civilian', by that I mean that the majority of members were mobilised into the RAFVR as soon as the war started. I wondered if there were any well above the age for service that, initially at least, kept the organisation going, but purely as civilians. Any ideas?