Embargoed to 0001 Tuesday February 3

The Royal Mint will weigh the smallest and the largest UK coins ever produced today as part of a quality assurance test that stretches back almost 750 years.

In all, 70,000 circulating and commemorative coins will be tested at the ancient Trial of the Pyx at Goldsmiths' Hall in London to assess the weight and quality of the work turned out by the Mint.

The smallest coin, which portrays Britannia, weighs a fortieth of an ounce, is eight millimetres wide and costs £50.

The largest is the Kilo Coin, which commemorates the centenary of the First World War and is 100 millimetres wide, contains a kilogramme of gold and sells for £45,000.

At the trial, first recorded in 1282, the monarch will be represented by the Queen's Remembrancer, who presides over matters to do with the Exchequer. An independent jury of City of London Liverymen from Goldsmiths' Company also attends the test.

At the trial jury members are presented with Pyx boxes, Pyx is the Roman word for chest.

A random selection of coins are then picked and weighed in wooden bowls. The test is then adjourned until May to allow time for trial coins to be tested by Goldsmiths' Assay Laboratory and the National Measurement Office.

In the past the penalty for coins failing the test has been severe. The master of the Mint - a role held by the Chancellor today - went to prison for six weeks in 1318 after poor tests.

Even Sir Isaac Newton, one of the world's greatest scientific thinkers, was at loggerheads with the jury during his time as master of the Mint when the integrity of his coin samples were questioned.

Deputy master of the Mint Adam Lawrence said: "The Trial of the Pyx is one of the oldest quality assurance trials in existence and is as important today as it has ever been, helping ensure integrity and confidence in our UK currency, commemorative and bullion coins."

He added: "The trial provides an opportunity for The Royal Mint to prove that our state-of-the-art technology and centuries-old hand skills remain second to none".

The Mid Glamorgan-based Mint estimates there were 28.9 billion UK coins in circulation at the end of March 2013, with a total face value of £3.9 billion.

It also produces currencies for more than 100 issuing authorities around the world accounting for approximately 15% of global demand.

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