Posts by Kate

As Change Checkers, we love it when new coins are issued. But how are they quality assured? And what processes do they have to go through before ending up in our collections or our pockets?

Since 1282, an independent procedure called the Trial of the Pyx has been responsible for ensuring that newly minted coins (both circulating and commemorative) meet the legal specifications for weight, size and metallic composition. The process takes place annually and can take 2-3 months to complete, but how exactly does it work?

Phase 1: The Opening

After striking, The Royal Mint randomly selects coins from each batch of denominations to be quality assessed. These coins are sealed in bags of 50 and stored in Pyx chests until the day of the trial.

On the day of the opening ceremony, the Pyx chests are transferred to Goldsmith’s Company Hall in London. The ceremony is presided over by the senior judge in the Court of Justice, the King’s Remembrancer, giving the trial the status of a Court of Law.

Did you know? The word Pyx comes from the Latin word ‘Pyxis’, meaning small box.

The trial jury, which is made up of Liverymen and more senior figures of the Goldsmiths’ Company, open each sealed bag of coins and place 1 into a copper bowl for testing by the London Assay Office, the remaining 49 are placed into a wooden bowl to be weighed.

Phase 2: Testing

The coins selected for testing are sent to the Assay Office where they are compared against a Trial plate. These metal plates, made of gold, silver, platinum, nickel and zinc, are held at the National Measurement and Regulation Office. The oldest surviving Trial plate, from 1477, resides in The Royal Mint Museum.

Next, the base metal and precious metal coins are separated, with the base metal ones going through X-Ray fluorescence spectrometry, and the precious metal ones sent for laboratory chemical testing. The main purpose of these tests is to break down the coins’ composition to check their metal content meets specifications.

Phase 3: Verdict

After rigorous testing, the Assay Office decide if the coins meet all specifications set out in the Coinage Act or by Royal Proclamation. Their recommendations are passed to the Senior Master and the King’s Remembrancer, who instruct the Goldsmiths’ Company.

The final verdict is delivered to the Chancellor of the Exchequer or their deputy and the Deputy Master of The Royal Mint.

The oldest judicial procedure in the country

The Trial of the Pyx dates back as far as the 12th century, making it one of the oldest judicial procedures in the country. As such, should the coinage be found to be substandard, the punishment for the Master of the Mint would be a fine, removal from office or even imprisonment!

Luckily however, modern coin production processes have become far more reliable, therefore the last Master of the Mint to be punished was Sir Isaac Newton in 1696. Newton was, of course, celebrated on the Sir Isaac Newton 50p in 2017, a coin that quickly become popular with collectors. Find out what makes this coin so interesting >>

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Did you know about this process? Or perhaps you’ve been lucky enough to attend the trial as a spectator? Let us know in the comments below!