Berlin Iron Work From 1796 to 1850 delicate lace-like jewelry was produced by Prussian Royal iron foundries from molten iron. In 1806 Napoleon defeated Prussia and took patterns from the foundry to Paris. Requests were made by the Prussian Royal family for donations of gold jewelry to help the war effort and in return citizens were given iron jewelry. The castings were treated with linseed cakes which left a black coating on the metal.