Quality index of silver is hallmark. The higher the hallmark the higher and better the silver quality and the more costly the coin made of this silver. The higher hallmarks are 945, 925, 903, 900, 810, 720, and 640. The coins with hallmarks under 500 are billons. They made of alloy consisting of silver and a base metal.

The reasons for using an alloy in coinage are: first - the hardness of alloy (remind that the silver is soft metal), second - the alloy make the coinage cheaper. It is possible …