Hi Alec,
I do not know that much about these pieces & have avoided them over the years due to my lack of knowledge on them. However, I do not like the example that you show because of the style of the maker mark on it. From what I can see it looks to be the known fake mark which is based on the Hermann Aurich mark. The correct mark should be a letter "H" sideways above a rounded, stylised "A". The fake mark blocks in the ends of the "H" to make it more like a rectangle with a line through the centre, or a capital "B" laying on its side...
There is not much about these in reference books or magazines, Littlejohn briefly mentions them in his book "Defending the Reich". He gives a very basic description, mentioning that there are variations of colour, but that is all. He states that it was probably first issued in early 1933 & had to be returned when the second more official version was introduced in June 1936 (the second version is the one with a black aircraft against a pale blue sky with Swastika flag below it). He does mention that the second version was issued by the Ministry of Aviation & was serially numbered, he does not say that the first version was numbered.
There is also an article in the April-May 2005 edition of the "Internationales Militaria-Magazin" #117, pages 12-13. This article is in German & unfortunately, I have not had the time to fully translate the article. However it does show a colour picture of one of these badges, one with a white aircraft & white enamel in the areas that yours is blue. It does say that there are copies with the fake Aurich mark which I have mentioned above.
Sorry that I cannot help more.
Cheers
Don