I received in the mail today another coin.  The chinese vendor is 
quite chatty in fractured english.  He is quite bent out of shape
that somebody left him negative feedback because the US postage 
was 57 cents and he charges 3$US for 'shipping'.  I told him to
make it 3$US 'shipping&handling' in future auctions.  He said
I was so nice that he would ship it for free.  I paid him the
3$US anyway as I didn't think he'd remember the emotional outburst
later.  He sent email on receipt of payment saying I have a 3$US
credit with him for future auctions. 

I paid less than 20$US (rather less) for a coin that is simply listed
as 'rare' in the catalogues.  The last time a coin of this specie
was auctioned was in the 1980s and was in poorer condition than
the one I just got in the mail.  It sold for rather more than
what I bid for it on eBay (you would have lost if you only bid 50K$US). 
I knew this while bidding and was just interested in adding another
'rare' coin to my book of counterfeit coins.  I knew full well what
I was getting especially as the vendor offered another of the same
coin prior to my receipt of my winning item and the only reason I
didn't bid on his other 'rare' coins is because I already have
numbers of fine counterfeits of those what he had listed.

I was wrong. I didn't receive a good counterfeit for my rogues
gallery binder.  I received a coin that I cannot prove is not
in fact as it claims to be.  Everything is 'right' about this
coin other than the price I paid for it.  This is scary stuff.

27 responses total.

By what means could you actually authenticate the coin if all outward 
indications are that it is not, as you supposed, a counterfeit?

This response has been erased.

Re calling people dumbasses:
"Please don't sound like a dumbass.  Instead, use an accepted notation for
denoting dollars."

This response has been erased.

How about US$20?

re#1: NMR would show if it is consistant with genuine item. Problem
is that genuine is scarce.  One would have to infer what a
'genuine' coin silver alloy would be of the time (late 1800s) which
is probably not real hard.  Not hard for the forger either.  First
off there are no cast mark around the rim.  It does in fact appear
to be a struck coin rather than a cast, and machine struck at that-
force perpendicular to surface, something a human cannot do.  It
does 'ring' like a silver coin and appears to be silver.  I may
want to rub the coin to test but not yet (rub coin on stone and
test with acids - pawnshop trick of the trade.  But it hurts the
coin a little, bad thing to do).  Turns out under a microscope there
are very faint signs of forging, not of the coin itself but probably
of the blank used to make the die from what this coin was struck 
(the original die is known to be in museum in britain, and prior 
to that in the possession of the british former general manager of 
the chinese mint also in britain so it was and continued to be in
england well prior to the Republic  (when many coins were 
'restruck' for various reasons).

The die was probably worked then used to strike coins that were
then carefully worked (dremel tool?) to similate wear and hid as
much as possible 'tells'.  The interesting thing is that someone
probably had access to an original in order to make this copy.

In addition, there is a large amount of hand labor involved - or
very high tech nc machine work (not as likely but then again
given the chinese fondness for 'dual use' military tech...).

All that effort to produce a coin that is so obviously rare (it
was in fact once thought to have never circulated).  If such is 
so casually and well done, it does make you worry about what more 
common 'affordable' coins are being produced as well.  If one 
were buying coins of this type (asian 'crown' or 'dragon dollars') 
that one might reasonably expect to be on the market it might pass
muster on first or even second glance especially if the weight and
dimensions were correct and it 'rang true'.

Like I said, scary stuff.

-------------

Re: "20$US"  Dunno, I use that notation a lot.  
I see (##)(currency symbol)(country) enought to
think it is a general practice.  For example, in the PRC you
will often see 1$US=8.1234$rmb (rmb is pinyin abreviation for 
'peoples money', but same idea)  

If the die has forge marks, then that should make a "unique" fingerprint
that would be very hard to duplicate.  Weighing the coin ought to give
you its density, which would allow you to recognize at least bad fakes.
X-ray crystallography might tell you something interesting about the
coin, that a forger might not know how to duplicate.  I suppose an
electron microscope might be interesting as well.  I don't know if
there's a way to make a non-destructive spectrograph of silver; would it
have absorption lines as a solid metal?

You can determine its density in the manner that Archimedes is alleged
to have done for the King's crown. This method eliminates the necessity
of measuring an accurate volume. 

Uh, the original die had no 'forge marks'  and yes, the microscopic
'forge marks' on the this (and similar) struck coins are a 'tell'.

Originally with 'monetized' money, a 1 yuan coin regardless of
mintage would for example contain 1 yuan's worth of silver by weight
and purity (often the purity was listed on the coin itself).  
Thus the common practice was to 'short weigh' - produce coins that
contained less than the official 'value'.  Thus usually you could 
tell contemporaneous conterfeit because it was lighter in weight 
than it should have been.  Ironically, genuine coins were often 
melted down to produce the counterfeit - or coins of countries that 
often used debased metal such as mexico.  The trick was to produce
something that looked and 'rang' true enough to circulate.  In old 
china you even had 'banks' or larger mercantile groups that marked 
the coins either physically or in ink so that they could tell coins 
that had been tested true and test those that hadn't (then of course 
you forge the 'chops').  It is only when the neumismatic value of 
the coins exceeded the 'monetized' that the production of replicas
become an issue.  Thus we are getting to the point where merely 
weighing or NMR spectroscopy (or similar) is not enough.  The 
bulgarians are destroying the market for greek and roman (and other
european) antiquities by their hi-tech reproductions.  It looks like
the chinese are well along the path of doing the same for asian.

(rcurl slipped in with an irrelevent comment.  It is current practice
of the bulgarians to produce coins of the proper 'specific gravity'.)

SO this one is a definite forgery?

Re #9: go jump in a lake (and we will determine your density, or lack
thereof). I was responding to mdw in #7, who suggested weighing the
coin to determine its density. My suggestion simplifies doing that,
without judging its utility, as mdw also did not. 

re#10: Yes. 
re#11:  It is getting to the point that even determining specific
density or spectrogram is not going to be enough (bulgars and
now maybe the chinese are seeing to that).  With a coin what's
value is far in excess of the base metal it has only been lack
of necessity that causes the modern forger to not properly match
the original coin.  

Laser cut dies are the next level and they are rumored to be 
in use.  I don't know where this all is going other than to 
destroy the market for these coins, and thus perhaps an incentive
for dealers to ignore the issue as long as possible.  Lets say
for example the value of the coin is 100$US.  It costs the forger
about 5$US per coin to produce.  He wholesales it to a network for
25$US.  lets say it costs 100$US to do a hi-tech 'certification', 
to slab and register 'good' coins (to 'chop' them) or determine
modern forgeries.  Is the 'good' coin now worth 200$US?  I
don't think so.  (is it not now a target for the forgers to 
produce the package of a 'good' coin along with the forgery?  
This is already being done by the way.  (Think software piracy
for a much larger market with similar problems))

Would isotopic composition be able to distinguish originals and forgeries?

Hmm...I heard somewhere recently that steel made before the 1940s is in
demand for some instrumentation applications, because it isn't contaminated
with radioactive fallout from bomb testing.  (A company recently salvaged a
sunken German sub for exactly that reason.)  I wonder if the same small
amounts of radioactivity are captured in other metals?  If so, that might be
another way to identify modern forged coins.

In doing isotopic signatures of metals it does't much matter if the
isotopes are radiactive or not, except that the radioactive ones allow
additional comparisons through their daughters. Archeologists are now
using these methods to determine the origins of objects, because every
ore has different isotopic composition.

Yes, and for the same reason forgers of historical documents search
libraries to steal blank pages from old books, some clever coin 
forgers are 'remanufacturing' valuable coins from contemporanious. 
Isotopically these coins would be correct I believe.  Consider 
melting two 1910 lincoln pennies to produce a blank which is then
struck using a lasercut die made from an original 1909SVDB to
produce a forgery.  From a materials standpoint the coin would
be dead on.  Hopefully the die marks of the result would be
microscopically different enough to detect.  But what if the 
manufacturing process for the counterfeit die were extremely
accurate to the point of reproducing such die marks?  Hopefully
the necessity of using digital controlled machinery would leave
a signature as well.  But you see where it is going, the forgers
get feedback to refine their forgery staying one step ahead of
the detection of the forgery.

Then what if the forger has access to the original die?  For example,
there are a number of chinese silver coins from the early republic
days that would undoubtedly be worth a lot more neumsmatically if
it weren't for the fact that the ROC even before it fled the mainland
and for sometime after was minting these coins from original dies
which had not been defaced as should have been - and out of original
material.  Sometimes mint engravers with a sense of propriety would
secretly alter minor details, sometimes not.  And consider that there
is a counterfeit mexican gold piece that is clearly struck at the
mint that is very difficult to detect - is a gold clad alloy coin of 
the proper weight and dimension.  Not too many people carry a hand 
held cat scanner or nmr spectrograph with them to coin shows...

the 1909 SVDB is a surprisingly common "coin".  virtually all of the
original mintage of 484,000 was "saved" (withdrawn from circulation
by collectors etc) and there are many more thousands of fakes residing
in collections.

Yes, and it is well within the price range of the coins the
bulgarians seem to be targeting right now.  Perhaps it is only
the familiarity of the lincoln penny to collectors that causes
them to avoid it and other US coins.  My point was as an example
of one of the many clever methods forgers use to produce their 
product to fool the experts -use the original metal.  

One of the other criteria that is used to judge authenticity of
ancient coins is toning and/or patina.  This is the natural 
chemical process the metal of the coin undergoes over a long
period of time and exposure to the elements.  As coins are often
buried the process is different than metal exposed to the open
air and since obviously the forger is interested in bringing his
product to market a bit sooner he has to find a way to simulate
the natural process.  Sometimes paint is used which of course
is another reason for 'cleaning' coins.  Each method however 
often had a signature.  For example, bathing the coin in a 
chemical bath would produce uniform toning or patina unlike the
more random natural process.  So you spatter a little wax on
the coin first, then one chemical bath, spatter again, then
another different chemical, then remove all wax and bathe in
a third chemical.  It produces a semi-realistic appearance 
however has a signature of its own.  Some years ago somebody
discovered that growing a culture of a particular mold or
fungus (no, I'm not gonna tell yah, you have to look a little
on the Internet if you are interested) would produce a random
patina that was really excellent and had none of the obvious
tells.  THe culture grew in a truely random fashion and was
quite active in quickly providing a nice patina that looked
good, wasn't uniform, and wasn't 'blobby'.  It was quite awhile
before that too was figured out  (unfortunately not before 
some embarassment of some who should have known better).

So, the lesson one can take from all this is?  I don't know.
Caveat Emptor?  Perhaps - or as one ebay 'dealer' that seems
to auction only the finest in rare chinese coins but "doesn't 
know much about them" put it "the buyer knows best".  I'm sure
it is possible to purchase a truely rare coin at a bargain
price, but I'm just as sure that it is as common as the coin.

Received two 3-tael sychee from australian antique dealer. One 
supposedly from tang dynasty.  The dealer in his item text
said he couldn't attribute authenticity.  Sychee are silver bullion.
The difficulty in authenticating these is that the authentic are
cast and thus a clever fake could be cast from a mold of an original.
They pass the tongue test.  My dealer friend thinks they are fake
but isn't quite sure why - he hates these type of things.  I think they
are 'faux' merely because I purchased them for significantly less
than the price for the base metal.  They are the correct weight,
but unfortunately that is a range and lead is heavy too although
these 'look silver'.  The fact that I purchased them 'cheap' might
be because american bidders (vast majority) are not as likely to bid
on auctions of foreign sellers - I don't usually unless I am looking
for a nice counterfeit or replica. Another candidate for NMR.

If they're cast from a mold made from an original, there could be some
interesting size distortion.  If they don't allow for thermal expansion,
the resulting ingot may be larger or smaller in size.  If the weight is
right, then either they were very smart about thermal expansion, or
there could be weirdnesses along some edges.  If there are imperfections
in the mold, such as sand, bubbles, etc., then that could result in
further differences - a cast of a bubble is not likely to turn out quite
the same as the original bubble.

Re #7:  You could do a non-destructive assay using something like
X-ray fluorescence, but you'd need to test an awful lot of stuff
to pay for the gear.

Maybe somebody in a university in Chicagoland does metallurgy and
would be willing to test the coin out of academic curiosity?

Actually, a friend has offered NMR and I may do that at some time
in the future for the sychee.  The problem is the sychee could only
be eliminated if it contained little or no silver, and counterfeit 
but probably contemporanious if the silver content was below 
about 40%.  The coin in question is obvious modern replica for
two reasons, at the time nobody would fake a coin that didn't
circulate much (remember, the purpose at the time was to pass it
in normal day-to-day commerce) and it is very well made but contains
forging marks -something not present in a milled or minted coin.

(response to way above:  X-ray crystallography would NOT be an appropriate
method for testing coins!  EXAFS (absorption & scattering) might work, but
I don't think it'd tell you exact ratios.  NMR seems like a singularly 
clunky way to go about determining composition, but at least it's non-
destructive--most chemical methods I can think of (e.g. elemental analysis
or ICP) would involve sacrificing bits of it.)

I wonder how you use NMR to inspect the interior of an object
which is metallic and thus protected from the RF probe coils
by the Faraday effect.  X-ray fluorescence has no such handicap.

(Okay, I agree that NMR could certainly detect differences in
isotopic composition in the layers it can inspect, but the
self-shielding nature of a metallic object still looks problematic
for inspecting the composition of the interior.)

I actually purchased a modern replica off an ebayer who was
taken by a seller.  It had an NMR spectrograph showing no
silver content whatsoever - mostly copper-nickel.  Yes, 
specially with coins the non-destructive test is the one
to use, thus weight/dimension and microscopy up to now.
Clever fakes require more clever detection and NMR looks
like a good bet for composition- but unfortunately is well
beyond most collectors (not everyone has friend with access).

I'm not very well up on solid-state NMR, particularly of metals.  But #24
has a valid point.  Seems like too much metal to be effectively studied by
magnetic resonance.
I don't think it'd be great at isotopic composition determination, 
necessarily.  For one thing, each isotope you study has to have an NMR-
active nucleus and I believe each separate NMR active isotope needs its
own frequency.  You can't accurately determine the ratios of different 
isotopes (or metals, for that matter) either, so far as I'm aware. Ya gotta
figure that whatever isotopes are present in one coin are probably also
present in a fake; it's only the ratios that change.
That said, I find I know astonishingly little about determining metal
compositions in a metal.  I'd pretty much have to take a sample and dissolve
it in order to apply most of the techniques I'm familiar with.

Someting you don't want to do with coins is anything that effects
the coin, especially appearance.  It is generally enough to determine
that there is no silver in what should be a .900 silver coin to 
determine it is a forgery.  A .900 silver coin might still be
forgery. Isotopic analysis would not determine a forgery made
from contemporaneous material from the genuine article -indeed that
is somewhat of a small problem, some forgers make more valuable coins
out of genuine but less valuable.  Thermoluminescence I believe is
of value in articles such as pottery - and the potters have taken to
grinding up old pottery shards to either glaze the item in places
where samples are likely to be taken, or incorporating into the
base clay.  I'm not sure how well it would work against reworked
genuine coin.  The presence of radioisotopes from nuclear testing
and fallout in the coin might seem promising, but the necessary
cleaning perhaps destroys much of the value and the cost of testing
probably renders it useless.

Right now, the Mark I eyeball (and tongue) -assisted perhaps by
optical enhancement (even a simple jewelers 5x loupe)-along with
a good scale and calipre or even ruler (or dimensional chart) 
are unfortunately probably the best tools.  That and the knowlege 
of what the coin should look like, and sometimes even feel like 
or sound like.  That and common sense.

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