According to the law regulating the manufacture and sale of precious metal is recognized as an official marketing gold 375 mil, also popularly known as 9 carats. Countries with higher levels of wealth than our market their products in nine carat: United States, Germany, Britain and Canada. It is mandatory for items with two brands of contrasts. The contrast of origin that identifies the manufacturer or importer and contrast contrast official warranty or guaranteed by the law of 375 thousandths. Therefore they can be legally marketed in Spain, identifying them in the stands and displays to the public, about 9 carats or 375 thousandths. The only difference between 18 carat gold (750) and 9 carat gold is basically the price being between 40-50% cheaper than 9 carat (375).