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How to detect a fake coin

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Valued Member
United States
344 Posts
 Posted 06/23/2013  4:28 pm Show Profile Bookmark this topic Add plonker to your friends list Get a Link to this Message

I thought to come up with simple set of steps to determine if a coin is a fake or not. Most of these information is learned thanks to this forum. Please feel free to point out additional information / corrections and I will update these steps.

1) compare the coins characteristics such as designs/inscriptions with a known good coin.

Inspect the shapes of the letters and digits as well as the details of the design.

Any publications such as Krause or following web sites can be used to find a known good coin.

NGC world price guide
http://www.ngccoin.com/poplookup/Wo...e-Guide.aspx

Numista
http://en.numista.com/index.mobile.php

Coin facts wiki
http://www.coinfactswiki.com/wiki/World_Coins

ANS
http://numismatics.org/


2) compare the weight and diameter of the coin with a known good coin

Again the above resources in 1) will help to find out the specification of the original coin. Underweight coins with little wear may be suspicious.

[need feedback in what can be considered as a safe % to be off ]


3) inspect the edge of the coin and compare it with a known good coin for inscription or patterns

Numista and ANS usually has the edge information such as the inscription. Search this forum for specific coin types such as Spanish 8 reales where this has been extensively discussed.

A seem along the outside edge may indicate a combining two dies and hence a fake. In addition letters on the edge showing signs of being in-scripted after the rest of the coin is made may indicate a fake.


4) For silver coins do the ring test and magnet test

Silver coins should not be attracted to magnets. Use neodymium magnet for testing

Balance a silver coin on the tip of your forefinger. Then gently tap the coin with a pencil or pen so that the coin on your finger does not fall. True silver gives off a long resonating high pitch ring.

[need help here to verify if this resonating sounds depends on the purity of the silver , 90% , 83% etc..]


5) inspect the surface of the coin
look at the surface of the coin and look for bubbles that would indicate cast copy. Also mushy and less sharp details may indicate a fake.

Reference
http://www.pcgs.com/News/The-Fundam...tion--Part-1

[needs more indications here]


6) specific gravity test for silver coins

A brief demo is here,
http://www.coincommunity.com/forum/...PIC_ID=39666

[Some what difficult to do and needs any recommendations on specific commercial kits available]

Pillar of the Community
United Kingdom
1036 Posts
 Posted 06/23/2013  5:32 pm  Show Profile Check Pertinax's eBay Listings Bookmark this reply Add Pertinax to your friends list Get a Link to this Reply
This has all the makings of a very good article and that's where it should be ultimately.

I suggest, too, in the UK; take or send by special delivery (with a stamped addressed special delivery envelope) your coin to the Dept of Coins, British Museum (London). Although they won't give you a certificate of authenticity, they will give you their opinion and they have a great collection and collectively, the staff have a lot of experience. It's also free (up to 10 items).

In Paris, France, the Bibliotheque Nationale provided a similar service 40 years ago (I spent a whole summer holiday there) and probably still do.

In the UK, the major coin auctioneers will normally give a free opinion on authenticity and value.
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Australia
11144 Posts
 Posted 06/23/2013  9:28 pm  Show Profile Bookmark this reply Add Sap to your friends list Get a Link to this Reply

Quote:
Use neodymium magnet for testing

Any old magnet will do - even a weak, wimpy magnetized plastic fridge magnet would be good enough for the purpose. Using a super-strong neodymium magnet can even give a false positive, because a super-strong magnet on a piece of silver can show diamagnetism (a repulsive effect). Though, again, you can use diamagnetism to test a suspect coin if you have a known genuine piece to compare it with, as outlined in SteveCaruso's article.

Quote:
Balance a silver coin on the tip of your forefinger. Then gently tap the coin with a pencil or pen so that the coin on your finger does not fall. True silver gives off a long resonating high pitch ring.

[need help here to verify if this resonating sounds depends on the purity of the silver , 90% , 83% etc..]

I've never found the "ring test" to be reliable, especially with Chinese fakes; they've found the secret to mimicking the "correct ring" in base metal. A coin's ring is basically determined by its dimensions (diameter and thickness) and the density and physical properties of the metal (toughness, elasticity, etc) it is made from.

A thick coin like an Indian hammered rupee will not ring, even if made of good silver (.917 fine); a coin that is damaged or has an air bubble trapped inside it can "sound fake", even though it is indeed genuine; an ancient Roman silver coin would have "crystallized" over the millennia, with changes to the internal structure of the metal changing the sound it makes. On the other hand, I've seen many times on the forum people posting "obvious" Chinese fakes who insist the coins must be genuine because they "sound just like a silver coin does". Like this fellow, for example.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
Pillar of the Community
Australia
8710 Posts
 Posted 06/23/2013  10:17 pm  Show Profile Bookmark this reply Add sel_69l to your friends list Get a Link to this Reply
Calgary Coins of Canada has an excellent series of lecture notes on the
identification of fake ANCIENT coins.
I have read them all in detail, some hours of commitment is needed.
Edited by sel_69l
06/23/2013 10:23 pm
Pillar of the Community
Hong Kong
722 Posts
 Posted 06/24/2013  09:31 am  Show Profile Bookmark this reply Add wonghinghi to your friends list Get a Link to this Reply
Thank you plonker, you introduce a systematic way to led a collector learns how to work out a fake coin. Though this never involves any particular skillful techniques, practice makes perfect, I believe it will work and help to avoid a great majority of low grade forgery.

Pertinax, you said

Quote:
I suggest, too, in the UK; take or send by special delivery (with a stamped addressed special delivery envelope) your coin to the Dept of Coins, British Museum (London).


Can I also send my coins to British Museum for investigation from Hong Kong? You know I can't send a stamped addressed envelope to them. Is there a link to elaborate the steps to access this service? Henry
Pillar of the Community
United Kingdom
568 Posts
 Posted 06/24/2013  11:31 am  Show Profile Bookmark this reply Add Tom Goodheart to your friends list Get a Link to this Reply
I'd add one more which is along the lines of 'know your coins' and that's that coins are unique.

If you find a coin that has all the same surface tell-tale marks, wear, lettering imperfections (I'm thinking mainly older coins here) as another then it's time to be alert.

While it may be that a coin hasn't sold after all, or that the original owner has parted with it,... but it could be that it's a direct copy. Or, in my experience, they are both copies and there's a scam going on.

Obviously, unless you can track down the other identical coin it's difficult to be 100% certain. But I've been fooled enough times (and I tend to think I know my stuff!) to be wary.

And the coins I'm thinking of are good metal, correct weight and unlikely to raise suspicion unless you know there are copies of such issues around.
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United Kingdom
1036 Posts
 Posted 06/24/2013  1:26 pm  Show Profile Check Pertinax's eBay Listings Bookmark this reply Add Pertinax to your friends list Get a Link to this Reply
wonghinghi,
The detail about their object identification service is at
http://www.britishmuseum.org/about_...ication.aspx

I've no idea whether they would provide this service abroad; probably a good idea to contact them (see http://www.britishmuseum.org/about_...act.aspx)and ask.

I think you'd need to provide sterling for return postage; foreign currency exchange here is notoriously expensive.
Edited by Pertinax
06/24/2013 1:26 pm
Pillar of the Community
United States
2584 Posts
 Posted 06/24/2013  3:56 pm  Show Profile Check TJsCoins's eBay Listings Bookmark this reply Add TJsCoins to your friends list Get a Link to this Reply
Great info!
Pillar of the Community
United States
1215 Posts
 Posted 06/25/2013  11:34 pm  Show Profile Bookmark this reply Add Numismat to your friends list Get a Link to this Reply

Quote:
Though, again, you can use diamagnetism to test a suspect coin


In my opinion this is one of the most reliable methods. You can build a magnetic slide relatively cheaply and by timing how long a coin takes to slide get an idea of precious metal content.
The only drawback is that copper will exhibit similar electromagnetic effects to precious metals. But again you can compare to a known example with equal metal content to what the suspect coin is supposed to be.
Pillar of the Community
Australia
8710 Posts
 Posted 06/26/2013  10:49 am  Show Profile Bookmark this reply Add sel_69l to your friends list Get a Link to this Reply
There are data bases on fake coins with which you can compare a suspected fake, and
there are services out there which you can pay for, for a 'professional' opinion to be passed on a suspected fake.
HOWEVER,
I find it a bit frustrating that there is very little published information that tells you specifically HOW to identify a fake coin. This is the sort of information that should be in the hands and minds of ALL collectors, investors and students of numismatics.

How else are you expected to gain experience to expose fake coins for yourself?
Pillar of the Community
United States
764 Posts
 Posted 06/26/2013  3:33 pm  Show Profile Check colonialjohn's eBay Listings Bookmark this reply Add colonialjohn to your friends list Get a Link to this Reply
Personally speaking I think the new book I have been working on recently with Robert Gurney and Gord Nichols on the Portrait 8 Reales Contemporary Counterfeits is a book if the casual collector or serious numismatist reads it cover to cover will self-educate the individual on how to properly determine fakes both Modern and of the period (Contemporary Counterfeits). The book will be published sometimes in mid/late 2014 and its a book on contemporary counterfeits written at a level never seen before in the numismatic marketplace. You can hold me to this claim. I remember going into see the President of the American Numismatic Society and Roger Hoge making this exact claim. It does talk about all the points made by Plonker and ... then some. If you like to collect contemporary counterfeits, avoid purchasing modern Chinese fakes or simply just collecting the legitimate issues without PCGS/NGC/ANACS holders this book will provide you "indirectly" the information you need to make better purchases of regal issues. I do read the counterfeiting columns in Coin World but who is going to remember on this date/denomination for the U.S. piece look for this small die break here, this misformed in Liberty, etc ... there are easier ways and some may be asking the seller to send you edge shot images, weight, diameter readings, etc.. The book also discusses the modern Chinese fakes and what compositions they are made of and how to avoid these issues. The book will also for the first time have two CD's in the rear pocket(s) with over 1,000 digital plate coin photos. A first ... PLONKER ... buy this book and if does not answer or more appropriately give you all the tools to avoid purchasing counterfeits (modern & contemporary - of the period) I will refund your money! .

John Lorenzo
United States
Edited by colonialjohn
06/26/2013 3:37 pm
Pillar of the Community
France
1303 Posts
 Posted 06/26/2013  3:53 pm  Show Profile Check MathieuMa's eBay Listings Bookmark this reply Add MathieuMa to your friends list Get a Link to this Reply
Collonialjohn : I will only buy it if both you and Bob sign my copy :D

I think many are waiting for that publication actually - and I think it's a great idea to take time to publish it and have it as perfect as possible.
For example to avoid comments like Proctor's on that ANA publication which was supposed to be a reference : http://www.amazon.com/Cobs-Treasure...w_p_t_1_E4X3
Pillar of the Community
United States
616 Posts
 Posted 06/26/2013  4:34 pm  Show Profile Bookmark this reply Add tokenmast to your friends list Get a Link to this Reply
To catch newer off metal fakes. While some/most can be found with refrigerator magnets only about 1/2 of the ones I handle can be found with those.(or 15lb pull.retriever magnet )
Not all fakes will fail test. Just ones with a Ferromagnetic, or Para-magnetic metal alloy at a high % in them will stick/pick up.

You can build your own array Extremely powerful with 9 or 16 n40+ (5mm or 10mm )cubes in it.
Arranged in a checkerboard pattern N/S/N/S and backed (epoxied)to a mild steel plate. I like to use a Chinese coin (for the irony )
2 tests of the magnets power.
A completed array will pick up a silver war nickel ( 9% manganese) or US paper money (magnetic ink)
If your magnet can not do this it is not powerful enough to catch some magnetic fakes. Not all off metal fakes are magnetic however, and a different class of instrument is required like XRF, Specific Gravity, or TFDwall.

The coin is a force, TFDwall. TrueField Detective . .. Tools and Instruments.cr.tm.pat/pend. Counterfeit/off metal, silver
Pillar of the Community
France
1303 Posts
 Posted 06/26/2013  4:57 pm  Show Profile Check MathieuMa's eBay Listings Bookmark this reply Add MathieuMa to your friends list Get a Link to this Reply
tokenmast : can you post a picture of your array ? I suppose you are talking about neodymium magnets ?
Pillar of the Community
United States
616 Posts
 Posted 06/26/2013  5:13 pm  Show Profile Bookmark this reply Add tokenmast to your friends list Get a Link to this Reply
Sure. Funny In this case the genuine one is lifted up! 9% manganese

The one on right is a Henning nickle. Both 1944

The coin is a force, TFDwall. TrueField Detective . .. Tools and Instruments.cr.tm.pat/pend. Counterfeit/off metal, silver
Edited by tokenmast
06/26/2013 5:47 pm
Pillar of the Community
France
1303 Posts
 Posted 06/26/2013  6:21 pm  Show Profile Check MathieuMa's eBay Listings Bookmark this reply Add MathieuMa to your friends list Get a Link to this Reply
Very interesting, it's a good way to get some metals which shouldn't be there.
And I learned that manganese was magnetic !! :D
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