Precious metal "precious" metal can also be determined by high demand or market value. Precious metals in bulk form are known as bullion and are traded on commodity markets. Bullion metals may be cast into ingots or minted into coins. The defining attribute of bullion is that it is valued by its mass and purity rather than by a face value as money. The level of purity varies from issue to issue. "Three nines" (99.9%) purity is common. The purest mass-produced bullion coins are in the Canadian Gold Maple Leaf series, which go up to 99.999% purity. A 100% pure bullion is
Commodity money modern commodity markets, although they use a sophisticated range of financial instruments that are more than one-to-one representations of units of a given type of commodity. Since payment by commodity generally provides a useful good, commodity money is similar to barter, but is distinguishable from it in having a single recognized unit of exchange. described the establishment of commodity money in P.O.W camps. Radford documented the way that this 'cigarette currency' was subject to Gresham's law, inflation, and especially deflation. In another example, in US prisons, after smoking was banned circa 2003, commodity money has switched in many places to