Der Stahlhelm, Bund der Frontsoldaten - World War I Frontline Veterans' Association
Beautifuly patinated enamel badge issued in 1932. The enamel is nice, only dirt is visible around the helmet.
On the back, there is a silver hallmark "935" and the marking "STH", i.e. Stahlhof (Magdeburg), which refers to the headquarters of the association.
Also, the marking "Ges.Gesch" = Gesetzlich Gesützt" i.e. protected by law.
There is no membership number, date of entry, or district engraving on the back, so it is either an unissued piece or a secondary copy of the owner.