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Moderator
 United States
23522 Posts |
Quote:
Last month I went into a pawn shop and bought several Morgans that looked in decent shape. When I took out a magnet, they were not attracted to the magnet but it did "push" them around, which even surprised the owner. Were those fakes? I spent way too much on them, $30 each, considering silver dropped to nearly 18/troy oz yesterday. I would say they're F to VF, no important dates. Silver is diamagnetic, which is to say that it creates a weak opposing field to an applied magnetism. I've never really researched it, but especially if the magnet being applied is a strong one, I'm not totally surprised that it might "repel." We normally test such coins by bringing the magnet to them vertically, or vice-versa, since you don't really have to let the magnet touch the coin to feel the attraction; I've never tried approaching it from the side on a flat surface to test it. |
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Pillar of the Community
United States
648 Posts |
What exactly is happing when a person feels something with a magnet and a coin? A very good question . There are laws to describe the forces. It is not simple. Quote:
Quote from the Wikipedia Faraday's law (and many more)
Some physicists have remarked that Faraday's law is a single equation describing two different phenomena: the motional EMF generated by a magnetic force on a moving wire (see Lorentz force), and the transformer EMF generated by an electric force ( due to a changing magnetic field (due to the Maxwell- - "Faraday equation). OR We know of no other place in physics where such a simple and accurate general principle requires for its real understanding an analysis in terms of two different phenomena.
- - " Richard P. Feynman, The Feynman Lectures on Physics
Very deep but not very helpful if you want to know if the coin your holding is real. Yes silver is diamagnetic,  as is water. (frogs can float in a very strong field) Bismuth is 18 times more diamagnetic than silver, still not helpful. Try graphite or pyrolitic carbon 1000 times more. the highest known, so much so that it floats over an array of magnets. No friction. Very skittish . Not slowed down. Eddy current may be the best working theory. Silver has the highest conductivity, copper very close. Conductors resist moving magnets by producing an electric field (why generators/motors work) Think of a coin as a small section of wire. When a moving magnet come close it resists by making An opposing field. The faster you move it the stronger the force. You can pull or push a coin a round a table with a very strong magnet. A useful test. Or you can slide it down the face of a coin, (slows way down)also a good test  Damping effect, aka magnetic braking. To make this effect repeatable and precise enough to say tell a Henning nickel from a genuine one. You need a platform that, protects the coin! And eliminates the variables. What a TFDwall does. Edited by tokenmast
06/22/2013 09:01 am
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Pillar of the Community
United States
1796 Posts |
Every single coin listed on The Black Cabinet (as well as roughly twice as many in the uncatalogued stacks) passed at least once as genuine before they ended up in the collection.
Fakes being sold as genuine are epidemic.
The diamagnetic ("opposite") pull exerted upon silver only happens when the magnetic field is in motion, which is why if you have a very strong neodymium magnet, you can "pick up" a silver coin with it. However, once the coin's velocity matches the magnet's velocity, the pull equalizes and it won't "stick." To get it to "stay" there, you'd have to pull the magnet away from the face of the coin at a constant acceleration (which is quite high).
However, this is useful for telling apart non-magnetic fakes as you can take a smaller neodymium magnet and slide it down the surface of the coin through a flip. If it's a slow slide, it's silver (or another diamagnetic material). If it slides off quickly (like with brass) you know it's the wrong metal. :-)
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Pillar of the Community
United States
648 Posts |
Quote:
take a smaller neodymium magnet and slide it down the surface of the coin through a flip. Great point steve The other guides you have on the Black Cabinet site are excellent also  |
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Valued Member
United States
127 Posts |
This thread has me checking and rechecking every coin in my collection. I just bought a BU 1941 Merc and I bet I've looked at that thing under the loupe with suspicion about 100 times lol.
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Valued Member
Spain
134 Posts |
I'm rather worried too since I read the post about the fake Mercuries. Is there any tip you can give us to spot the fake ones as easily as you; what do you usually look for?
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Pillar of the Community
United States
648 Posts |
To catch off metal fakes. While some can be found with refrigerator magnet only about 1/2 of the ones we handle can be found with those.(or 15lb.retriever ) Not all fakes will fail. Just ones with a Ferromagnetic, or Para-magnetic metal alloy at a high % in them will stick. You can buy an array from us or build your own array with 9 or 16 n52 (5mm or 10mm )cubes in it. Arranged in a checkerboard pattern 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. |
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Valued Member
United States
293 Posts |
Any key date coin that you see on ebay like a 1909-S-VDB 1c or a 1916-D 10c or an 1893-S $1 you need be naturally suspicious when the coin is raw (i.e. NOT certified by either PCGS, NGC, or ANACS) and when you don't know the seller because Red China is knowingly allow their people to fake these. Some of these fakes are so good they fool numismatic experts. Once you've done enough business with the seller and its obvious that he/she has a at least a strong regional presence at the show business (i.e. a bigger fish dealer from Minnesota would work all the shows in that state, western Wisconsin if not the whole state parts of Iowa and Fargo and Sioux Falls in the neigboring Dakotas) then you know you are working with a dealer that should be able to catch most of the bad fakes before they even buy them themselves. |
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Bedrock of the Community
United States
19963 Posts |
Quote:
you need be naturally suspicious when the coin is raw (i.e. NOT certified by either PCGS, NGC, or ANACS) You need to be suspicious about ALL coins. I've seen fakes in TPG slabs and, of course, there are also fake slabs. If there's a way to steal money, some piece of garbage will do it. Fakes are just a part of collecting and they will always be. In fact, IMO, it's getting worse every year. The dealers I know will tell you hundreds of stories each about fakes they've seen. Edited by BadThad
06/29/2013 02:26 am
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Valued Member
 United States
154 Posts |
Makes me wonder how many coins in my collection aren't real. The legacy I intend for my son might just be worth half of my imagined value!
And what's with silver dropping to $18! Is this a good time to buy?
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Bedrock of the Community
United States
17884 Posts |
It is if you think it will go back up, it isn't if you think it will keep dropping. What it is actually going to do is anybody's guess, and many of them will be wrong.
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Valued Member
Spain
134 Posts |
The prices of silver coins near bullion value have been dropping along silver, but silver coins with higher premiums are a different story; I would say they even kept going up this last year.
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Pillar of the Community
United States
1796 Posts |
Quote:You need to be suspicious about ALL coins. I've seen fakes in TPG slabs and, of course, there are also fake slabs. Just to back BadThad's comments up, say "hello" to Morgan:  "Hello, Morgan." :-) |
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Pillar of the Community
United States
9792 Posts |
Don't forget the fakes that are so good that the rest of the numismatic world traded, bought and sold them for years before being proven to be fakes. The 1907 St. Gaudens Double Eagle - the Omega copies (now worth quite a bit themselves) The Micro "o" Vams of 1896, 1900 and 1902 http://www.pcgs.com/News/Pcgs-Decla...CounterfeitsThese were not proven to be fakes until 2005, though I believe as far back as the 1960's they existed. "Buy the Book Before You Buy the Coin" - Aaron R. Feldman - "And read it" - Me 2013! ANA Life Member #3288 in good standing since 1981, ANS, Early American Coppers Member (EAC), Colonial Coin Collectors Club member (C4), Conder Token Collector Club member (CTCC), Civil War Token Society (CWTS) member, Liberty Seated Collectors Club (LSCC) & Numismatic Bibliomania Society member (NBS), USMex, Member in good standing, 2¢ variety collector. See my want page: http://goccf.com/t/140440 |
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Bedrock of the Community
United States
17884 Posts |
The micro O's are probably contemporary counterfeits from the early 20th century. There is at least one article from back around the turn of the 20th century that warned of counterfeit New Orleans dollars and the diagnostic them mentioned was that they had a very small lowercase O mintmark. (At that time silver had dropped so low that even using full metal weight had less than 50 cents worth of metal in them.)
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Posted 06/22/2013 08:47 am
