Hallmark date letters

Precious metals, such as gold and silver, are generally too soft and malleable for practical use. They are therefore mixed or alloyed with other harder metals. Hallmarks provide proof of an article's precious metal content, and older items should feature a date letter to denote the year it was hallmarked.

British hallmarks date back to medieval times. In 1757, counterfeiting hallmarks was made a felony and punishable by death. Traditionally, common control marks consisted of four punches: maker or sponsor mark, proportion of precious metal or fineness mark, assay office and the year of testing.

The UK Hallmarking Act (1973) updated the law for the modern era, and requires all gold items over one gram (1g) to be hallmarked. Hallmarking must be administered by recognised assay offices. The 1973 act removed the date from the compulsory marks. This left just the fineness, assay office and maker as standard marks. Despite this, the year punch is still often included, but date letters are much less common these days.

Gold hallmarks date letters

Today there are four UK assay offices: Birmingham, Edinburgh, London and Sheffield. Before these current locations, there were offices in:

• Chester - closed 1962
• Exeter - closed 1883
• Glasgow - closed 1964
• Newcastle - closed 1884
• Norwich - closed 1702
• York - closed 1858

There was also previously an office in Dublin - formerly part of the UK system - that is now an independent Irish Republic office. Somewhat confusingly, each assay office had their own date letter hallmarks at various times, which can make identifying the year difficult.

To save the space used in hallmarking, the year is indicated by letters of the alphabet. In order to avoid any confusion, at various times either one of the letters "I", "J" and "L" have been omitted. Therefore each period of alphabetic sequences consists of 25 letters, not 26. The alphabetic sequences are also differentiated by changes in typeface, punch shape, and changes from upper to lower case characters.

The system of letters has changed over time and there have even been local variations between the various assay offices. The hallmark years have also not always been calendar-years, that is January to December. Confusingly, hallmark years have changed at dates such as the month of a monarch's crowning or assay officers' terms of service.

The Birmingham Office, for example, which opened on 31 August 1773, traditionally changed letter on July each year. The London office, with its iconic leopard’s head punch, used to change years in May. Under the 1973 Act, these variations have been abolished and standardised across the UK. From 1975, all Assay offices have the same date letter which changes in January.

Below is a comprehensive list of hallmark date letters going back to 1900.