Prussian Imperial Air Force Observer Badge. Type Wilhelm Deumer.

Solid tombak/brass based and in an excellent, absolutely unworn condition with all of the silver plate still present, the high points burnished and the enamel without damage.
Not marked but a known variation that has been attributed to the company of Wilhelm Deumer from Lüdenscheid. See Carsten Baldes, Abzeichen und Ehrenpreise der Fliegertruppe 1913 – 1920 p.259.
Probably manufactured in the late 1930s, early 1940s as a replacement piece for former observers in the Imperial Air Force.
From a recent small hoard find of a uniform or LDO shop.