In medieval times great emphasis was put on the weight and fineness of the King’s coinage. Control was vital – after all, the task of producing gold and silver coins provided endless opportunities to defraud the Crown.
At the time of the Domesday survey, the coins received at the Royal Treasury in payment of taxes were tested by weight alone. Trial plates of known fineness were introduced formally in 1477 although they were most certainly used in connection with the re-coinage of 1247 against which coins were tested and this remains the method of testing today.
Apart from the troublesome business of assaying, gold could also be reliably tested by touch-stone and this was the day-to-day practice at the Royal Mint throughout the Middle Ages. Remarkable accuracy could be achieved by an experienced man, for in addition to the stone itself, the Royal Mint kept a set of ‘touches’ called needles consisting of 647 pieces of gold of varying alloys. The gold to be tested was streaked across the stone and the resulting mark compared with that made by needles of known fineness.
It was vital to get it right: in 1318 when the alloy was found deficient, the Master of the Mint was put in prison. When in 1423 the Master could claim that his coins were finer than ever before, he was admonished, the Commons pointing out that making the money better than it should be ‘would cause it to be broken, melted again, or borne out of this land, for the advantage that may be had therein, for goodness of the alloy’. It was a fine line.
Times may have changed – coins in circulation no longer contain any gold or silver – yet, in the age of the vending machine, the need for consistency in the weights and dimensions of UK coins remains of paramount importance.
Gold and silver trial plates, in a virtually unbroken sequence from 1477, are a treasured part of the Royal Mint collection.