Counterfeit Gold, Counterfeit Silver

DoChenRollingBearing

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One of my blog readers today sent me a link to a video (Portland, OR TV station) about fake Chinese gold and silver showing up here in the USA. I then asked three of my own blog readers (two scientists and one coin dealer) to advise me how to easily and quickly determine if a gold (or silver) coin is fake or not.

Much of the video concerned NUMISMATIC fakes though. Here's the link to the video:

http://www.shtfplan.com/precious-metals/chinese-counterfeiters-flood-global-markets-with-fake-silver-and-gold-100000-coins-from-a-single-counterfeiter_11102011

I got the below responses:

1) Thomas is a scientist:

Hi Robert,

The simplest way to test silver is to listen to the acoustic properties. Take a coin and flip it. It will have a nice ring to it. Lead alloys have a dull thump to them. Try flipping a silver quarter, then flip a new quarter. The difference is pretty striking, and it can't be faked by any method I know of.

For gold, the best way is to test the density by measuring the weight and the volume. Of course, there are now tungsten fakes supposedly floating around. Sonic testing would probably work here as well, though I have never tried it myself. It is my understanding that this is the way they test gold bars these days. (they use a computer, though). But you should be able to hear the difference pretty easily.

-Thomas

2) Doug is a scientist:

Sure, Bob, I like talking to smart people no matter how met. You can
pass on my info if you like.

Re the counterfeit. The old acid test, mentioned in the vid helps with
the surface of course, and isn't too hard to do. But I'd assume that
since electroplating is pretty cheap and easy, the surface would pass
that test...still worth doing since it's so easy I suppose, and it would
only damage fakes anyway.

Weight alone is better than nothing, but of course you want to measure
volume too -Archimedes to the rescue! You can see how much water some
coins displace in a graduated cylinder for example, and make sure the
density is correct - that will detect lead cores etc.
Tungsten cores (since the density is close) are harder - but tungsten is
a heck of a lot harder than almost anything - a spring loaded center
punch or bend test should take care of that one pretty quick.

More subtle might be the alloying of some other metal, which in small
amounts wouldn't show up easy in the density test, but would show up in
the acid test if there was much of it (and it was a base metal). I'd
think you could see the color difference if any amount of say silver was
added to gold with the eyeball.

Else you're down to more destructive testing - melting point, scraping
with a knife to see below the surface and so forth. Ultrasound will
only work on fairly thick stuff, because the transit time in metal is
really fast.

And of course, here in my fusion lab, I could to radio-activation and
look at the resulting gamma spectrum....but since most activations make
mostly beta rays, and only incidental X rays, you'd primarily be testing
the surface metal, not the whole thing.

3) Lewis is a coin dealer (the fisch products are a clever fitted balances to check dimensions and weight of various PM coins):

http://www.fisch.co.za/orderonline.htm#pricing
http://www.fisch.co.za/operation.htm
http://www.onlygold.com/TutorialPages/Coin_specsFulScreenVersion.htm
http://about.ag/JohnsonMattheySilverBars.htm
http://www.coinweek.com/commentary/...le-bullion-cash-transactions-or-lack-thereof/
http://news.coinupdate.com/irs-and-...quirements-for-coin-and-bullion-dealers-0353/
See what you can use from the above links.
LEWIS
 

pmbug

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The US Mint publishes the dimensions for all of their coin products, so you can measure yours with a good caliper (~$20 at amazon). You can also measure weight with a good scale that measures troy ounces (~$12 at amazon).
 

white&yellow999

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another test you can do is the Specific gravity test. Pretty easy to do at home. Also attached the magnet test which is pretty cool and you can maybe blow your friends minds because of the Di-magnetic property of silver.


 
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Unobtanium

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WRT fake coins, if you buy from ebay or from some other person-to-person transaction, there is a reasonable chance that you could end up with a fake.

Even if you buy from a coin shop, there could be a reasonable chance that you could be dealt a fake coin.

However, does anyone know if the chances are near-zero that you would get a fake coin from a very reputable online dealer? Do these reputable dealers check every coin that they acquire for future resales, or do they only spot check their incoming inventories?
 

ancona

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Noob here with a couple of ways to test. The first way is the oldest way and that is water displacement as noted by WY999.

However, most large recycling yards have an instrument called an XRF, which uses X-ray fluroscopy to determine the type and purity of metal. They will charge a nominal fee for the test, but it is worth it. My firm has one we use for other purposes, but I frequently spot-check rounds for purity, especially generic stuff.
 

DosZap

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I suppose, and it would
only damage fakes anyway.

I have heard this will (Acid test) spot real coins.So I would not use it on numismatic/semi numis coins(until you verify what I was told).
 

Jjack

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When it comes to coins i would never do any destructive tests even dropping it to test for how it rings.
From my experience:

  • Make sure the image on the coin matches description exactly (simplest test).
  • Using a Loupe check to see if the mint mark and lettering match. Also check the sides see if there is no gaps of silver or gold (tell tell signs of plating).
  • Do the Weight and measurements (use a caliper) match the specs.
  • Feel of the coin (using cotton gloves). How does the coin feel is it rough, smoth etc and compare that with a real coin.
 

DoChenRollingBearing

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Jjack, your comments more-or-less match what a local coin dealer told me, that can EXAMINE the coin and know.

That is useful information, thanks for passing it along. I bought a digital scale (good to 0.1 grams), an El Cheap Chino, but it works OK.

And since the GREAT BULK of what I own is American Gold Eagles (and Silver Eagles), I can check the OD very easily by putting them right into the US Mint tubes.

I still would like to find a device that is not insanely expensive so that I could check coins better (ultrasound, etc.).
 

bushi

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The simplest way to test silver is to listen to the acoustic properties. Take a coin and flip it. It will have a nice ring to it. Lead alloys have a dull thump to them. Try flipping a silver quarter, then flip a new quarter. The difference is pretty striking, and it can't be faked by any method I know of.

For gold, the best way is to test the density by measuring the weight and the volume. Of course, there are now tungsten fakes supposedly floating around. Sonic testing would probably work here as well, though I have never tried it myself. It is my understanding that this is the way they test gold bars these days. (they use a computer, though). But you should be able to hear the difference pretty easily.
This is BRILLIANTLY simple, and seems to be working all right (although I don't have any fakes to compare to - but tested on regular coins)! I love that guy!
 

pmbug

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I got an email from the Fisch people. They have just announced a new "wallet" with testers for various silver coins:
The new Fisch are included with the Silver Dollar Fisch to make:

Wallet #6 - Silver
  • U.S. Silver Dollar (1840-1935) (Excluding Trade Dollar)
  • American Eagle (1oz.)
  • Maple Leaf (1oz.)
  • Vienna Philharmonic - Austria/Guernsey 8 Double (1oz.)
They also have a new website: http://thefisch.com/
 

pmbug

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rblong2us

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Wow this is a real vintage thread !

Look at those post dates and joining dates and this has to be one of the first threads on here.

Are there more hidden treasures like this ?
 
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