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 Indian rupee discontinued but continued to be the legal tender. In Series IV, 5 paisa and 20 paisa coins were discontinued though they continued to be minted in Series III till 1994 and 1997 respectively. 10 paisa, 25 paisa and 50 paisa coins were minted in Stainless Steel. 1992 onwards, 1 Re coin was also minted in Steel and Rs. 2 and Rs. 5 coins in Copper Nickel were introduced. The very considerable costs of managing note issues of Re 1, Rs 2, and Rs 5 led to the gradual coinage of these denominations. These coins continued to be minted till 2004,