Zinc Luftwaffe Flak badge, with "GWL" manufacturer mark on the back (Gebrüder Wagerhoff, Lüdenscheid)
The integral setup is working perfectly.
The front and back of the badge have the so-called "GWL cracks", which are hairline cracks that occur during production due to heat.
Mainly visible with a magnifying glass, and which also serve as a kind of identification point.
Rare type!