The ‘old’ pound coinSee all questions about commodity
Hi I’m Lizzie and I’ll be your Commodity Consultant today,
1) Making the strip
A nickel brass alloy is poured into the casting equipment where it is set solid between two slabs of water cooled graphite. This continuous moulding process produces an endless strip of metal, because of the heat the metal has reacted with oxygen in the atmosphere and has gone all black so tools are used to scrape the surface clean with the aid of a white lubricating fluid. At this point the metal is still far too thick and so it must be squeezed between rollers working under ENORMOUS pressure. Precision rolling produces a strip that is exactly as thick as a pound coin should be wound up like a wash spring.
2) Making blanks
Next the metal is headed into the mouth of a blanking press which apparently sounds like a machine gun! (fingers best avoided with this one). The real joy of this press is around the back, here these little discs begin to look familiar – they still haven’t got the queens head on them yet, but they soon will have!
Metal is a pretty tricky material because the more you push it about the tougher it gets, this is called work hardening so before the blanks can get the queens profile they have to be cooked in an annealing oven. After a good long bake the metal is malleable again which means that it’s soft but the heat has oxidised the surface again!!!!!
A bath with abrasive ball bearings provides the answer, a cauldron filled with a solution of sulphuric acid works a charm. After twenty minutes the shine is restored again. The acid is washed off and the ball bearings fall through a sieve to be recycled. Now the shiny blanks dance into the drying chamber.
The the old days criminals would clip coins around the edge so that they could sell the precious metal leaving the poor old coins getting smaller and smaller! By pressing a pattern into the edge of coins they are decorated and protected from clipping! Still to come is their obverse and reverse pictures (aka heads and tails).
3) Design and die making
Next the coins make their way to the engraving department. The pictures and writing that we see on coins are created by patterns of relief (ups and down – have a feel with your finger!). Engravers skilfully cut a three dimensional coin into a block of plaster – which in years past would have functioned as a model to make a hard metal copy known as an electrotype. The pattern on the electrotype would then be reduced on one of the mints magnificent old Janvier machines. As the electrotype rotates the design is traced by a fine metal point fixed to one end of a pivoted bar, at the same time the movement of the tracer is scaled down onto the tip of a tiny spinning cutter. Over the course of several days the cutter produces a reduction punch from which working dyes will be made.
After more than one hundred years of service the Janvier machine has now been replaced by more modern technologies, this update happened through a round ruby tipped probe scanning an original plaster model, a digital recording of every tiny movement was then transferred into the memory banks of a computer. The record of the scan can then be used at any time by a cutting machine (it may be faster than the Janvier but boy does it make a racket!)
4) Striking coins
Coins can be struck using hydraulically controlled equipment with the weight of a blue whale behind them! Such high pressure pounding produces a coin that is almost perfect in every way but will take far too long to create coins that are in mass circulation. For these there is a machine which works at a much sharper rate! 25,000 coins can be produced by one machine every hour.
These beautiful, shiny new coins are wrapped and stacked before being taken away for storage in ‘the long room’ (aka a burglars dream – a room stacked to the ceiling with cash!) before making their way to their new homes.
The Royal Mint estimates that around 2.5% of £1 coins in circulation are fake and in a 2009 survey, 99% of these fake £1 coins found in cash centers were made of a nickel-brass, of which three fifths contained some lead and a fifth were of a very similar alloy to that used by the Royal Mint. The remaining 1% were made of simple copper-zinc brass, or lead or tin, or both.
So how is The Royal Mint making the new pound coins to stop this forgery!?
Apparently it’s a secret….
At the heart of its originality, Gordon Summers, the chief engraver at The Royal Mint, explains, is a top-secret, "high-security feature", which he can't give away the details of. "It's something you need a machine to detect." He added that this feature is only being used on coins by the Royal Mint, but says it has been used on bank notes previously. "It is currently impossible for those counterfeiting coins to copy – it's not difficult to do, it's impossible". Since the new pound coin was released, speculation has been rife about how this feature works. It is believed that the top layer of metal on the surface contains pigments that form a "secret binary code", invisible to the naked eye. The code can only be read using a specific frequency of ultraviolet light installed in the Royal Mint's special fake coin detection machines.
Although I can tell you that the new pound coin is Bimetallic, made of two metals. The outer ring is gold coloured (nickel-brass) and the inner ring is silver coloured (nickel-plated alloy).
Slightly off topic but really interestingly the old pound coin began circulation on the 21st April 1983 after it became apparent that with the general decline in purchasing power, the £1 unit of currency was more appropriate to a coin than a banknote. The note was in constant use on average lasting only nine months, whereas a coin can last as long as forty years or more! To make the pound easy to identify, the £1 coin is thicker than other coins, while the ‘yellow’ colour helps it stand out from the cupro-nickel ‘silver’ coins that were already in circulation. The weight of the coin was decided largely on the grounds of cost and the need to allow for higher denominator coins in due course.
The pound coin is 22.5 mm in diameter, weighs 9.5g, and is 3.15mm thick. It is composed of Nickel-Brass, specifically 70% copper, 5.5% nickel and 24.5% zinc, and it has milled edges.
Follow this link to see how the coin faces of the pound coin have changed through the years http://www.royalmint.com/discover/uk-coins/coin-design-and-specifications/one-pound-coin
Thank you for your excellent question!