6C These Carbon coins are made of compressed coal dust by the C. Conradty factory, which made carbon electrodes for arc lamps. They are surprisingly hard and not crumbly, most likely due to whatever binder is used. This coin is about 35mm diameter and 5mm thick. During post-WWI German hyperinflation, and due to metal shortages and coin hoarding, Notgeld ("emergency money") was issued in a variety of materials (paper, cardboard, rubber, wood, even porcelain) by private organizations. (JM3)