I've read a heap of German stuff over the years and nothing else comes close to this that I can recall... in terms of an actual advertisement.

From the date, I would not be in the least surprised if a Stormer airgun looks very much to be made of English parts. Most all of the repeaters that we can actually date to that era are made with the standard English parts (Baler/Currie.) In 1804, England was still doing a great deal of business in Germany. It wasn't until 1806, sitting victorious in Berlin, that Napoleon declared his Continental System banning all English manufactured goods.

Hopefully a Stormer can be found. No matter what, it should be interesting.

Dates of airguns. If memory serves, the oldest known airgun is circa 1760, in the Kremlin; a present to Empress Elizabeth, and it is an air cane.