The illustration is of a gold trial plate of 1560, from the reign of Elizabeth I. But what is a trial plate? Amongst other functions it was used in a ceremony known as the Trial of the Pyx which was and is an assessment of the quality of the work of the Royal Mint. These days the trial takes place annually at Goldsmiths' Hall, London and although circulating coins are no longer made of gold or silver the formal verdict is still an important quality standard that the Mint has to meet.
The origins of the trial lie in the Crown needing to have a means of verifying that the Master of the Mint was making coins that were of the correct weight and fineness. If too little gold or silver was being put into the coins the Master would be defrauding the people and possibly making a generous profit for himself, whereas if too much gold or silver was being used he would be putting the Crown to needless expense. A trial plate was an independently agreed standard to which the Master of the Mint was required to work; coins had to be made to the same standard as the trial plate and there were severe penalties if the coins were found wanting.
As part of the Mint's normal production, a certain number of coins would be put to one side and stored in a secure box known as the Pyx. At a trial, the Pyx would be opened and a number of coins assayed to find out how much gold or silver they contained. A small piece would also be clipped from a trial plate and it too would be assayed so that the fineness of the coins could be compared against the fineness of the plate.
The unusual shape of trial plates, with their jagged or indented outline, represents a further safeguard in the system to ensure that neither Crown nor people were defrauded. A plate would be made to the agreed standard and it would then be cut into a number of portions, two, for example, going to the Mint, one to Goldsmiths' Hall in London, while the central portion would be retained by the Exchequer. At a trial of the Pyx a Mint portion of the plate, to which the Master will have been working, would be presented and, because the original plate had been cut in a distinctive fashion, its authenticity could be established by fitting it into the central piece kept by the Exchequer.
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The Trial of the Pyx dates back many centuries and in 1837 a series of trial plates was transferred to the Royal Mint from the Pyx Chapel in the cloisters of Westminster Abbey. The Chapel had long been used as a secure store by the Exchequer and it contained many ancient relics, including old coinage dies. In January 1843 there was a further transfer of material from the Pyx Chapel. In this second collection was an unusual silver ingot of 1278 or 1279, which has sometimes been described as the earliest surviving trial plate, although there is a good deal of doubt as to whether it was in fact actually used in this way. The earliest surviving trial plates are instead likely to be the gold and silver plates of 1477.
Forming a virtually unbroken series from 1477, the series of trial plates received from the Pyx Chapel in 1837 included the gold plate of 1707 which had been the cause of a dispute at the Trial of the Pyx in 1710. The plate of 1707 had in fact been made too fine and, to the anger of Sir Isaac Newton, then Master of the Mint, the jury reported the coins to be below standard. Newton was able eventually to secure withdrawal of the offending plate and a return to the 1688 plate, of which only a tiny fragment was to be found among the items transferred in 1837. Unusually for an ultimate standard, a trial plate is consumed as it is used and new plates have therefore to be made periodically.
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