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 Australian dollar to as 'silver' though actually 75% copper and 25% nickel, and for many years there were also "bronze" 2¢ and 1¢ coins. The 50¢ coin originally had a circular shape, and contained 80% silver and 20% copper, so that the material of the coin was worth more than 50¢. It was made to almost identical dimensional specifications as the British 2'6 pence half crown. However, to avoid confusion among the round coins, and because of its excess value, it was only produced for one year then withdrawn from circulation; there were no 50-cent coins minted for 1967 or 1968. It