Current UK Hallmarks
In the Uk there are currently four hallmarks for silver which has to be applied to any jewellery item weighing over 7.78 grams:-
.925. This means there are 925 parts of silver in 1000 parts of the metal or in other words 92.5% of the metal is pure silver. It is referred to as sterling silver and is the most common format for use in jewellery since the proportions are perfect for design and strength.
.950- Referred to as Britannic silver this means it is 95% pure silver.
.999 as you would expect means 99.9% of the metal used is silver. It is a relatively new hallmark and currently is seldom seen in jewellery usage.
.800 is 80% silver and is sometimes referred to as Mexican silver although a lot of the Indonesian snake chains are made using only 80%. The main disadvantage is that it will tarnish faster than sterling silver and is slightly yellow and duller.
In the 12th century the English King, Edward I, decreed that silver should be tested for its quality and refinement. He also ordered that a mark should be stamped on the silver to confirm that it had passed this test. This test was called an assay and gave birth to the modern assay offices and hallmarking systems.