DE is an abbreviation in this wiki referring to Deutschland (Germany).
Patents are registered in Germany at the German Patent and Trade Mark Office, called in German the Deutsches Patent- und Markenamt; abbreviated as DPMA.
Below patents, there was and is another tier of intellectual property protection called Gebrauchsmusterschutz; Gebrauchsmuster are lighter-weight alternatives to patents that give shorter-term protection and aren't evaluated as stringently by patent examiners. (An English patent expert called them "Protection of Useful Designs".)
Foreigners submitting patents in Germany were required to use a patent agent. (However, in most cases we don't know who the agent was; names of agents do not appear on the scanned patent originals we've been able to see.)
To receive a patent, an invention had to be new, defined as never before used in the German empire or explicitly described by publication. The submitter of a patent did not have to prove that he had invented the concept (though a patent would be disqualified if the idea was demonstrably stolen from the true inventor.)
Patentees had the sole right to make, use, and sell their inventions. Infringement could be punishable by a fine worth ~£250 or imprisonment for up to one year.
Thompson writes: "German patents are published often immediately after application". Therefore it would seem that we cannot exactly equate the date 'Ausgegeben' with the 'date published' except insofar as the latter applies a final approval of the patent. (Though we also know a patent can be ausgegeben then gelöscht.)
Progress is being made regarding the legal and other roles played by Germany's precursor states, as pertinent to patents and otherwise, throughout the periods of early aeronautics, during which Germany, along with a few other nations, was undergoing extensive change, change particularly along the lines of unification. (See: Prussia, Bavaria ...)
This wiki has 816 German patents and 1,027 patents filed by Germans.