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  4. How do I design a system for detecting fake coins?
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How do I design a system for detecting fake coins?

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Offline techmind

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counterfeit coin
« Reply #20 on: 07/10/2011 00:28:03 »
By the way, something like 3-5% of one pound coins in circulation in the UK are forgeries, but they're close enough to the correct size/shape/alloy to work most vending machines and sorters. The usual give-away is the poor milling and lousy lettering on the outer edge, and a slightly softer (fuzzier) die image on the faces, and that the two faces may not have the correct alignment relative to each other. Many of the forgeries are becoming so good that you have to take quite an interest to spot them.

(See also: http://www.coinauthentication.co.uk/poundfiles.html       this page is a few years old - counterfeits have improved since many of the examples shown.  See also http://www.coinauthentication.co.uk/newsletter13.html#onepound )

I reckon the best hope the Royal Mint / Bank of England has of removing the majority of the present fake-pounds from circulation is some high-speed optical image-processing...



Also UK one- and two-penny pieces have been copper-plated steel for the past 6-7years or so, while the original ones from 1971 and through the 1980's were copper all the way through. The copper ones have (or are in danger of having) more value as scrap copper than their face-value.
« Last Edit: 07/10/2011 00:35:25 by techmind »
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Offline SeanB

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counterfeit coin
« Reply #21 on: 07/10/2011 19:36:47 »
That is why a lot of currencies have changed style. At the end of the production of the SA 5 cent piece in nickel, it was worth 6 times face value in scrap price alone. The new coins are a lot cheaper, and are not as durable. The nice thing is that the mint is defraying costs by making coins for other countries, and AFAIK we do make a lot of the low value Euro cents.
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