Fineness and fineness marks

What is fineness?

Fineness expresses the proportion of precious metal in an alloy, often in parts per thousand. 830 silver contains 83 per cent silver; 925 sterling silver contains 92.5 per cent. For gold, 585 and 750 denote 58.5 and 75 per cent gold. Other metals make up the remainder.

Fineness, carats and weight

Gold purity can also be expressed in carats, on a scale of 24. This use of carat must be distinguished from the unit of gemstone weight. As a calculation example, 100 grams of homogeneous 830 alloy nominally contains 83 grams of silver. The total weight of an object with steel blades, stones or filling cannot be used in the same way.

Interpreting a mark

A fineness mark states metal content. It does not by itself identify a designer or establish an object's age. Record the complete set of marks, including any maker's and assay marks. An unclear or suspicious mark requires further examination.

Silver plating

In silver-plated objects, silver is mainly present in a coating over another metal. EPNS is therefore not a silver fineness standard. See also silver.

Reference

Birmingham Assay Office: reading fineness marks in UK hallmarks. Each country's marking system needs its own interpretation.