A date letter is the part of a British hallmark that indicates the year in which a piece of silver, gold or platinum was assayed and marked. It takes the form of a single letter of the alphabet, set within a shield-shaped punch, and it changes annually according to a sequence specific to each assay office.
The London assay office has used date letters since the fifteenth century, and other offices adopted them at different times. Each cycle typically runs through around twenty letters before beginning again, with the style of lettering, such as Gothic, Roman or italic capitals and lower case, and the outline of the surrounding shield changing between cycles so that each year can be distinguished. Published tables of hallmarks allow collectors to identify the year by combining the date letter with the town mark and the shape of the shield. Historically the letter often changed partway through the calendar year rather than on 1 January. From 1975 the British assay offices adopted a uniform date letter, and since 1999 the date letter has been an optional part of the hallmark. Worn marks should be checked carefully against reference tables.
