The stamp inside a ring, bracelet or other piece of jewelry is used by the manufacturer to indicate the manufacturer's or designer's name, the metal purity and type. Called hallmarks or assay marks, there are a very large number but in terms of valuation, the most important deal with metal type and purity.
Silver purity is given in a numerical code, which refers to its purity across a thousand parts.
- 925 is sterling silver
- May also appear as: S. Silver, sterling, SS or 925/1000
- May be gold plated
Gold may be indicated as a karat weight, or K, or also as a numerical code referring to its purity over a thousand parts, based on pure gold being 24 karats.
- 10K - 10 karats; 14K - 14 karats; 18K - 18 karats; 22K - 22 karats, or
- 417 - 10 karats; 585 - 14 karats; 750 - 18 karats; 833 - 20 karats.
- Platinum - the other precious metal - is indicated as Plat. or 950 Plat.
Other metals use varying formats to indicate type. Base metals hallmarks only indicate the type of metal and not its purity.
- S.S. - stainless steel
- G.F. - gold filled like a gold shell filled with a base metal
- G.P. - gold plating over a base metal