Here is a totally cynical and skeptical thought....
"When the facotory was sold, this letter and the badges were found"...
Forget the fact that a box arrives somewhere and lays around with a letter for decades and noone thinks to open/distribute/use the stuff...
Think more along the lines of... here we have a factory that under contract makes and SELLS badges to the Luftwaffe/RLM.
They are ordered, paid for with state money and delivered.
They are distributed to the different Units.
They are phased out.
Then the factory writes to the units ! Says "You dont need them, can we have them back?"
And the commander says "Well, you charged us good money for them, they ARE govt property, most of the guys would like one as a souvenier, there is no reason off the top of my head that I can think of why you should get something back for free that you charged us for.... but OK, I will happily return stuff that you have no use for and will leave sitting around in a box for 50 years until it becomes a "Stash""
And off they go... with the Deutsche post... on Immelmann Geschwader expense...
Over the last 5 years many dealers at German Shows have Aluminium ones on the table. Most collectors I know are very skeptical, I know none who has bought one.
I dont "Know"... but it seems like it COULD be a well planned hoax....