Many coins and some bars are not made of pure gold or silver, but of an alloy. The pure gold content forms the fine weight. For example, the Krugerrand is made of a gold-copper alloy. Thus 1 oz of Krugerrand have a weight of almost 34 grams, but the fine weight, the pure gold content is 31.1035 grams. Consequently, a 1 oz Krugerrand has a fine weight of exactly 1 oz gold, its roughness is around 34 grams.