My feeling is maybe 5-10 were made and these were more than likey special order.
Hello, I have seen a list of about 120 luft generals and as we know some of them have been very vain and picky and I am sure some of them had more daggers and hangers than only one. So there should at least be more than 5-10 of these hangers around but nevertheless they are quite rare.
And you could be right with your idea that these were made only on special order.
Regards,