Crown gold is a 22 karat (kt) gold alloy used in the crown coin introduced in England in 1526 (by Henry VIII). In this alloy, the proportion of gold is 22 parts out of 24 - or 91.667% gold - and is appreciably less prone to wear than the softer 23 kt gold of earlier gold sovereigns - an important point for coin intended for everyday use in circulation.
The alloying metal in England was, and is, traditionally restricted to copper. This is still used for the current British gold sovereign. An exception was for the gold sovereigns of 1887, when 1.25% silver, replacing the same weight of copper, was used to gain a better reproduction the image of Queen Victoria for the Golden Jubilee of her reign.
Elsewhere, both copper and silver have been used in varying proportions.
In the United States until 1834, gold circulating coins were minted in 22 kt. crown gold - although using about 6% silver as well as copper.
The South African Krugerrand, first produced in 1967, is produced in the traditional crown gold recipe of 22 kt gold, (remainder copper), because it was originally intended to circulate as currency.
Most gold coinage nowadays is not designed for daily use and circulation, so the requirement for a hard alloy is much less - and such bullion coins are commonly of pure gold of 24 kt, 0.999, 0.9999, or even 0.99999 fine (see Canadian Maple Leaf).