The gold alloys commonly used in jewellery production belong to the gold/silver/copper trivalent system. Until the 19th century it was forbidden in Europe to alloy gold with other metals. This and the fact that these three metals also occur with each other in nature is the reason why the ternary system gold/silver/copper is used for the classic jewellery alloys. For this reason we also use the classic gold in the production of our Mokume Gane wedding rings. The colours of the alloy range from rich yellow, as in the case of the Mokume Gane wedding rings Abura, to light green and salmon pink to silver white. By adding further metals, the properties of the alloys are influenced according to the requirements. Fineness of the alloys: In Germany jewellery and utensils may be alloyed and offered in any gold fineness. Stamping of the fineness is not mandatory. In case of stamping, however, the legal regulations must be observed. The exact fineness of precious metals can only be determined in a laboratory. In everyday life, random samples are used to approximately determine the fineness of a gold alloy in 1000 parts of the total weight, i.e. in per mille. Other measures, such as solder and carat were in use before 1880. The fineness can be stamped into jewellery or utensils. Indications of fineness by engraving are not permitted. As a rule, goldsmiths usually use finenesses of 585 to 999 when making jewellery. For industrial production, the range is usually from 333 to 750.