25 Pfennig - Mülheim an der Ruhr

Issued by the city of Mülheim an der Ruhr in 1917, this zinc piece belongs to the vast Notgeld phenomenon driven by the wartime disappearance of copper and nickel coinage — metals requisitioned for munitions production. Hundreds of German municipalities issued their own emergency small change during this period, creating a fragmented patchwork of local currency that the Reichsbank tolerated out of necessity rather than policy.

Zinc was the default substitute, though it corrodes aggressively in circulation, which accounts for the difficulty in finding undamaged survivors from industrial Ruhr cities where humidity was rarely in a coin's favor.