It is a legal requirement in the UK for all jewellery containing precious metals to be hallmarked. It also gives you peace of mind that the precious metals i use are exactly what i say they are. All of my pieces are Hallmarked and here is an explanation of what all the marks mean.
A traditional Hallmark is made up of 5 symbols:
1: The Makers Mark ( mine is GB in a circle) This is unique to me, no one else will have or be able to use this Mark.
2: The Traditional Fineness Symbol. (in this instance the lion for Sterling Silver)
3: Millesimal Fineness Mark. (This mark tells you how fine, or what quality, the metal is, as well as indicating the metal type. This numerical format was introduced in 1999 and shows the precious metal content of the article, expressed in parts per thousand. We mark a piece to the lowest standard of alloy content, so it guarantees that the quality of the article is no less than the fineness indicated. )
4: The Assay Office Mark. ( Mine is the Lion as my items are sent to the Assay Office in London. Birmingham, Sheffield and Edinburgh all have their own individual marks)
5: The Date Letter Mark. (This is changed on January 1st every year. The font, case and shield shape all change so can only indicate one specific year.)