Trial of the Pyx (England)

The Trial of the Pyx was a public trial or test of the purity of gold and silver coins that began in the thirteenth century and continued into the present day. In 1982 Queen Elizabeth II and Sir Geoffrey Howe, chancellor of the Exchequer, attended the Trial of the Pyx in celebration of a custom marking its seven-hundredth anniversary. The oldest extant writ ordering a trial came at the behest of Edward I in 1282. Although similar tests were conducted at regional mints, the most meticulous and thorough tests were held for coins struck at the Royal Mint in London.
To conduct a trial a specified sample of coins of each denomination was set aside and stored in leather bags identified by the month of coinage. In 1485 a sample consisted of 10 shillings from every 10 pounds of gold and 2 shillings from every 100 pounds of silver. These leather bags were put in a chest, or pyx, hence the name “Trial of the Pyx.” The pyx was locked with three keys, one held by the warden of the mint, a second by the comptroller, and a third by the master-worker. The crown could call for a trial every three months, but the trials were much less frequent.
To conduct a trial, the officers of the mint appeared before the Council in Star Chamber, together with the lord treasurer’s clerk and officials of the Exchequer who brought the contracted specifications for the weights and fineness of coins. The pyx (or pyxs) was unlocked before the Council.
The Trial of the Pyx has always made use of the most advanced methods for assaying gold and silver, beginning in the earliest times with the use of the touchstone. A public jury of 12 lawful citizens and 12 members of the Goldsmith’s Company of London actually conducted the public testing. If the jury held the coins to meet the prescribed standards, based upon the fineness of the bullion sent to the mint by the Crown, the master-worker received a letter of acquittance. If the coins fell short of the required weight and fineness, the master paid a penalty to the Crown proportionate to the profits the master skimmed off by reducing the purity of the coinage. Of course, the king was never brought before a public jury to test the purity of the precious metal he sent to the mint. Presumably the mint master assured himself of the purity of the metal supplied by the king.
The custom of the Trial of the Pyx bore witness to the ever-present danger of debasement of the coinage, either at the hands of the Crown, or at the hands of dishonest mint officials. The longevity of the custom stood as a reminder of the importance certain groups in society, particularly merchants and bankers, placed on the trustworthiness of the coinage. The Trial of the Pyx helped the English Crown control the temptation to debase the currency, contributing to England’s reputation for sound currency and laying the foundation for England’s commercial success.

See also:
Challis, C. E. 1978. The Tudor Coinage.
Davies, Glyn. 1994. A History of Money.