Crown gold

Crown gold is a 22 kt (alloy, introduced in England for gold coin manufacture in 1526 (by Henry VIII) on the basis of superior wear properties, and perhaps to save the state mint costs. It is 22/24 = .91667 fine or 91.667% gold. Previously, gold sovereign coins were made from 23 kt gold, but this was soft and invited deliberate filing, and also non-intentional wear.