Exchequer Standard Troy Weights, 1824.
© Science Museum / Science & Society Picture Library
A set of nine gunmetal weights made by Bate of London, ranging in weight from from 30lbs to 1lb. Each weight is stamped on one side with its value in Troy lbs, and on the opposite side in Troy oz. They are also stamped with a crown and the words '1824 Bate London'. The troy weight system is used mainly for weighing precious metals and gems and is based on a pound of 12 ounces or 5760 grains. It developed from the Roman pound, or libra, which was made up of 12 uncias, or ounces.