In contrast to costume jewellery, genuine jewellery has a lasting material value and thus represents a permanent investment in addition to the optical aspect. Genuine jewellery can be described as such if it is mostly made of precious metals or if genuine jewellery has been processed in it. The most frequently used precious metals for genuine jewellery are gold, silver and platinum, which possess their high value because of the worldwide rare occurrence and are therefore attractive for the production of high-quality jewellery. Embossing, which provides information about the degree of purity of the material used, is indispensable for the classification of genuine jewellery. The stamp on a piece of jewellery is thus the unmistakable symbol for genuine jewellery. If a stamp is missing that reveals the gold, silver or platinum content within the alloy used, the authenticity of the piece of jewellery should always be doubted. The content of the gold used on such a genuine jewellery stamp is usually indicated in per mille, for example 18 K gold to 750 per mille consists of pure gold, while the rest consists of copper and other metals. The numbers 8 K, 14 K and 18 K are the most common characteristics of genuine jewellery with the respective gold content.