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 pound sterling coins' designs. As of 31 March 2016, there were an estimated 30.14 billion coins circulating in the United Kingdom. The first decimal coins were circulated in 1968. These were the five pence (5p) and ten pence (10p), and had values of one shilling (1/-) and two shillings (2/-), respectively, under the pre-decimal £sd system. The decimal coins are minted in copper-plated steel (previously bronze), nickel-plated steel, cupronickel and nickel-brass. The two-pound coins, and, as from 28 March 2017 the new one-pound coins, are bimetallic. The coins are discs, except for the twenty pence and fifty pence pieces, both of which