This provides information about the content of precious metal (silver, gold or platinum) in a jewellery item. For example, gold is a soft metal, which is why in the jewellery trade it is alloyed with other metals that make it harder and change its colour or even the surface.

The fineness accuracy is estimated at 0.001 of precious metal weight in the total alloy weight. Gold fineness of 0.333 means that in 1000 units of the alloy weight there are 333 units of precious metal. It means 8-carat gold. Gold fineness of 0.750 means 18-carat ore. In theory pure gold has the fineness of 1000/1000 but this is impossible to achieve. Therefore, the most precious gold of 24 carats has the fineness of 0.999.

For precious metal products to be legally offered to customers, they have to have a proper hallmark given by an Assay Office. Such a hallmark includes information about the ore the jewellery product was made from expressed by special signs as well as the fineness. For example, letter P means an Assay Office in Poznań. This does not apply to silver products weighing less than 5 grams as well as golden and platinum products weighing less than 1 gram. If a product is heavier but so delicate that a hallmark could damage it, the hallmark does not have to be used. In such a situation the jewellery receives a proper certificate that includes the information that could not be struck.