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Testing systems

A while back I found a neat coin tester on the Internet. I can't find it now, but it worked by testing shape/size and weight. It was a simple 'card' that had a pivot point on it and a well in which you put the coin. The size of the well fit the coin exactly and the card would balance if the weight was correct. This sort of thing would fit in a pocket and might be able to be made with a second well for a different size/weight.

We could/should also have one that does size/shape plus weight plus some electrical testing. Apparently conductivity changes when composition does. This sort of tester could be useful in a retail situation as it could be built to test multiple "coins".

It has also been mentioned that a register could be built that has the testing stuff built in. It can simply weigh the tray to give an accounting of the register's balance (and also tell if the cashier is stealing from it!). 

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Re: Testing systems

I found the tester I was referring to. It is the Fisch.

There is also the coin safe coin gauge.

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Re: Testing systems

Look into a system that generates a tone or something that creates a harmonic in the medallion, but only if it is pure.

...

Eli
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Re: Testing systems
Shouldn't this be doable with a postal scale (weight) and water in a measuring cup (displacement) and a chart?
Eli
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Re: Testing systems

Been a long time since I took chemistry. But shouldn't .999 silver have a specific density? Shouldn't 1 0z displace a certain amount of water?

 The default (chealp) testing system, given the correct numbers (if the above facts are accurate) could be a measuring cup of water and a postal scale.

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Re: Testing systems

The potential problem with this is that there are cheaper materials than silver that are more dense than silver. They can be used to create a piece that has the same overall density, but with less cost for raw materials.

Of course this would be prohibitively expensive in small scale counterfeiting operations, but if we get big enough to make it worthwhile then it might become a problem.

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Re: Testing systems

Just heard of another idea. Spanish Scientists Mod Optical Mouse Into Counterfeit Coin Detector - basically they have modified a mouse to scan coins to verify that the design is correct.

It, and the proposed webcam version, would probably do a good enough job on the design. However, I doubt it would measure the mass/weight properly, nor would it likely determine metal content. This isn't a problem with base metal coins since they are so cheap in the first place - all the cost and security is in the design - but it certainly is with precious metals and even large copper pieces.