Arnstadt issued iron notgeld coinage during World War I when the imperial government requisitioned copper and nickel for war production, forcing municipalities across Germany to improvise small-denomination substitutes from whatever base metals remained available. Iron was notoriously poor for coinage — it corroded readily in circulation and struck unevenly — which is precisely why surviving examples in decent condition are harder to find than their original mintages might suggest.
Arnstadt issued iron notgeld coinage during World War I when the imperial government requisitioned copper and nickel for war production, forcing municipalities across Germany to improvise small-denomination substitutes from whatever base metals remained available. Iron was notoriously poor for coinage — it corroded readily in circulation and struck unevenly — which is precisely why surviving examples in decent condition are harder to find than their original mintages might suggest.