I like early aviation poster stamps as well.
Unfortunately, there have been untold millions of cinderellas printed over the years and it would be impossible to put them all in one catalog. A Scotts type catalog of all of them would probably run hundreds of volumes.
The Gardiner and Greiczek catalog of just exhibition stamps, and only to 1914, runs over 900 pages.
https://books.google.com/books/abou...ilnwoQEACAAJYour blue Darmstadt stamp is listed in there with a U for uncommon rating

Charles Kiddle, the top expert on poster stamps, published a book on early aviation stamps, but only for Germany.