The system of samples of noble metals exists in order to be able to determine their content in alloys. Samples are used for branding jewelry. Having looked at the sample, the specialist can easily determine the proportion of the noble metal in one or another jewelry alloy.
According to Russian legislation, any alloys containing more than 30% of precious metals must have a sample and a corresponding stamp.
There are several sampling systems - metric, carat, lot and spool. In the metric system, the content of a noble metal is determined by the number of milligrams of it per gram of alloy. So, the 585th fineness of gold means that one gram of the alloy contains 0.585 grams of pure gold. The metric system in our country has been adopted since 1927 and replaced the spool system.
Spool samples have existed in Russia since the beginning of the practice of assaying precious metals. The purity of the precious metals was indicated in the spools. A spool is a unit of measure for mass in the Russian system of measures. If a coin weighed one spool and was made of an alloy containing 75 parts of gold, it had a 75th standard. It could be said that it was made of "75-spool gold". In the Russian weighing system, one pound was equal to 96 spools. The spool test indicated how many pure metal spools were contained in one pound of alloy. Therefore, gold of the 96th standard was recognized as the purest. It contained over 99.9% of the noble metal.
Officially, the spool system for gold alloys in Russia was introduced in 1733, and for silver alloys - in 1711. The most common samples at that time for silver items were 84, 88, 91 and 95, and for gold - 56, 72, 82, 92 and 94.
In medieval Europe, the lot system of samples was used to denote the purity of precious metals. It was based on the brand - the unit of weight for gold and silver. The stamp was equal to 249 grams and contained 16 lots. The lot was also a pre-metric unit of mass measurement and weighed about 12.8 grams. The lot test, set on a noble metal, indicated how many lots of pure metal are contained in one grade (16 lots) of the alloy. The lowest sample was a sample of 6 lots, and the highest was a sample of 16 lots.
In parallel with the metric system of samples, the carat system is now used in the world. This system is based on the carat - a unit of measure for mass, constituting 0.2 grams. A fineness of 22 carats means that the mass of the noble metal is 91.6% of the total mass of the alloy. The highest carat fineness is designated as 24 carats.