Commodity money cans or foil pouches of mackerel fish fillets, which have a fairly standard cost and are easy to store. These may be exchanged for many services in prisons where personal possession of currency is prohibited. In situations where the commodity is metal, typically gold or silver, a government mint will often coin money by placing a mark on the metal that serves as a guarantee of the weight and purity of the metal. In doing so, the government will often impose a fee which is known as seigniorage. The role of a mint and of coin differs between commodity money
Standard & Poor's Commodity Index Standard & Poor's Commodity Index The Standard & Poor's Commodity Index (SPCI) is a commodity price index that measures the price changes in a cross section of agricultural and industrial commodities with actively traded U.S. futures contracts, stretching across five sectors - Energy, Metals, Grains, Livestock, and Fibers & Softs. Only commodities that are consumed for industrial use are included in the index. Weights in the index are determined by the dollar value of Commercial Open Interest (COI) for each component commodity, and rebalanced annually each February. Effective January 31, 2008 Standard & Poor's discontinued calculation and publication of the