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 rupiah In 1963 Indonesia Issued a coin of 2 1/2 rupiah depicting Sukarno in two forms, one of the coins was intended for West Irian, the other was intended for entire Indonesia, but both coins were minted in very limited quantities. Their values according to Krause catalogue are US$290 for the first coin and US$100 for the Irian coin. While NGC online catalogue evaluate one of the coins as worth US$290. West Irian coin is evaluated as US$100, and never placed into circulation, maybe because of hyperinflation that ruled Indonesian economy in Sukarno era, especially during the years 1959 to 1965.