Metallurgical assay and the U.S. Mint continue to produce precious metal bullion coins for collectors and investors. The precious metal purity and content of these coins is guaranteed by the respective mint or government, and, therefore, the assay of the raw materials and finished coins is an important quality control. In the UK, the Trial of the Pyx is a ceremonial procedure for ensuring that newly minted coins conform to required standards. Metallurgical assay A metallurgical assay is a compositional analysis of an ore, metal, or alloy. Some assay methods are suitable for raw materials; others are more appropriate for finished goods.
Coins of the United States dollar term mill (or mille) was defined in the eighteenth century as of a dollar or 0.1¢, no coin smaller than 0.5¢ has ever been officially minted in the U.S. However, unofficial mill coins, also called "tenth cent" or "tax-help coins", made of diverse materials—plastic, wood, tin, and others—were produced as late as the 1960s by some states, localities, and private businesses for tax payments and to render change for small purchases. Coins of the United States dollar Coins of the United States dollar were first minted in 1792. New coins have been produced annually since then and they make up