On jewelry, "585" is a measure of gold's purity and indicates that the piece is made from 14-karat gold. This number is derived from the percentage of pure gold expressed as parts per 1,000. This system of certification is widely used in Europe.
Gold that is 14 karat is 58.3 percent pure. The figure is rounded up and expressed as parts per 1,000 giving 585 as the measurement. Gold that is 75 percent pure is described as 18-karat gold and is denoted as 750 in European hallmarking.
In the United States, the purity of gold is measured using the karat system. Pure gold is 24 karat, and this is the standard against which purity is measured. Gold that is 14 parts pure gold and 10 parts other metals is 14-karat gold.