The Museum is home to a spectacular series of gold and silver trial plates dating from 1477, these plates being the officially approved standards against which the composition of coins can be independently checked by comparative assay.
Browse highlights of the trial plates collection below.
The Royal Mint Museum has the best collection in Britain of gold and silver trial plates, many of them having come from the Pyx Chapel in Westminster Abbey in the 1830s. These plates are in essence thin sheets of metal from which samples could be readily cut for the purpose of conducting comparative assays to check the accuracy of the coinage.
A debate over which is the earliest surviving trial plate has been sustained for many years and it has centred on whether the item illustrated here, a late arrival from the Pyx Chapel in the 1840s, is in fact a trial plate or a piece of silver intended for some other purpose. On the basis of the impressions stamped into the surface it is possible to say that this ingot-shaped piece of silver dates from c.1279 and it is indeed the stamped impressions from coinage dies that immediately suggest a link with trial plates. In its dimensions and overall appearance, however, it is quite different. At over half an inch thick, it is unlike any other trial plate in the collection and the current thinking is that it should be regarded as some form of ingot, the precise function of which has yet to be determined.
The connection between a monarch and the appearance or nature of the coinage has waxed and waned over the centuries. Henry VIII, as well as being famous for influencing many aspects of national life, left his mark on the coinage by debasing it as a way of raising money. Silver in particular suffered, with the fineness being reduced markedly over the debasement period and, not only is the evidence to be seen in the coins, it is also there in the assayers’ trial plates that were made at the time
A trial plate is a way of testing the precious metal content of a coin. At less than 800 fine this one was made to a standard of silver well below the sterling fineness of 925 and shows the degree to which the arrangements for the debasement were formalised. The indented appearance of trial plates of the period makes them arresting-looking objects in their own right and as a series they represent a distinctive element in the history of the British coinage.
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