of England and the Kingdom of Scotland, Newton used his previous experience to direct the 1707–1710 Scottish recoinage, resulting in a common currency for the new Kingdom of Great Britain. After 15 September 1709 no further silver coins were ever struck in Scotland. As a result of a report written by Newton on 21 September 1717 to the Lords Commissioners of His Majesty's Treasury the bimetallic relationship between gold coins and silver coins was changed by Royal proclamation on 22 December 1717, forbidding the exchange of gold guineas for more than 21 silver shillings. Due to differing valuations in other European countries this unintentionally resulted in a silver shortage, as silver coins were used to pay for imports, while exports were paid for in gold, effectively moving Britain from the silver standard to its first gold standard, rather than the bimetallic standard implied by the proclamation. The coinage reform of 1816 set up a weight/value ratio and physical sizes for silver coins. Each troy ounce of sterling silver was henceforth minted into 66 pence or 5 shillings. In 1920, the silver content of all British coins was reduced from 92.5% to 50%, with some of the remainder consisting of manganese, which caused the coins to tarnish to a very dark colour after they had been in circulation for long. Silver was eliminated altogether in 1947, except for Maundy coinage, which returned to the pre-1920 92.5% silver composition. The 1816 weight/value ratio and size system survived the debasement of silver in 1920, and the adoption of token coins of cupronickel in 1947. It even persisted after decimalisation for those coins which had equivalents and continued to be minted with their values in new pence. The UK finally abandoned it in 1992 when smaller, more convenient, "silver" coins were introduced. History of decimal coinage Decimalisation Since decimalisation on 15 February 1971 the pound (symbol "£") has been divided into 100 pence. (Prior to decimalisation the pound was divided into 20 shillings, each of 12 [old] pence; thus, there were 240 [old] pence to the pound.) The pound remained as Britain's currency unit after decimalisation (unlike in many other British commonwealth countries, which dropped the pound upon decimalisation by introducing dollars or new units worth 10 shillings or pound). The following coins were introduced with these reverse designs: Half penny, 1971–1984: A crown, symbolising the monarch. One penny, 1971–2007: A crowned portcullis with