The Coinage Act 1870 (33 & 34 Vict. c. 10) stated the metric weights of British coins. For example, it defined the weight of the sovereign as 7.98805 grams (about 123.27747 grains). The Act was repealed by the Coinage Act 1971.
The Act also vested the title of 'Governor of the Mint of Scotland', which had ceased minting coins in 1707, to the Chancellor of the Exchequer.
A contemporary history suggests that the Act was influenced by the criticisms of George Frederick Ansell.
References
Coinage Act 1870 Wikipedia(Text) CC BY-SA