Two Very Rare Coins

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Swamperbob, Have you ever purchased a coin you thought was fake and it turned out to be real?

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BWAAAAAAAA! I almost inhaled my soda. Great question!

Ah those crazy asians. I wonder if they do requests?

Hey Bob. Do you see many copies of gold coins circulating out there?

snowman - yes the Chinese do take requests. If you supply the original there is a fellow from Tiawan who says he can create a pair of Steel dies for about $2600. He claims to be an expert engraver. Of course if you want ancients, Slavey takes requests but the starting price is much higher. But the forgers can create a limited use pair of plastic dies far cheaper and they would actually produce a better copy. I have heard of but never actually spoken with one of the guys who would produce a forgery on order. I communicate with them to learn about what they are doing but I do not engage in the trade myself.

Regarding gold forgeries - there are any number of them. Mike Fahey had a good article on a $20 fake last week in Coin World.

About four years ago I was given a group of 15 sovereigns for authentication. They were gold plated on copper fakes. Well done, die struck almost correct in weight but too thick. A couple had tiny nicks exposing the fraud. They were all MS 63 or so and from one die pair. That never happens. So I CUT one for the buyer. At my risk. He did get his money back.

Recently, I also saw a nice copy of a Mexican 50 Peso struck in 60% gold. The buyer had bought it encapsulated in a TPG slab (one of the fly by night outfits). Upon removal - the fraud was obvious - no edge design at all, far too thin and it was about half the correct weight.

About a month ago I got a high grade gold cast copy of an 1834 French 40 Franc for authentication. Weight was within a gram of correct as I recall and assay was about 75 % gold. These were made to evade the law when you could not import gold into the US except as "old" coins. Many were actually cast in 0.999 fine gold.

snowman - there are numerous possible gold alloy metals. The most common are copper and silver. Sometimes both are used in an unknown proportion and the heavy metals are also sometimes employed. So just which alloy is present is usually only determined after the item is assayed ( using a destructive test) or after an Xray Flourescence analysis (Non-destructive). The first method obviously damages the coin and is rarely used. The second method (which is also costly) does very well with the surface of the item but ONLY to a depth of a few microns. Sheffield Plates can not be thus detected.

So when you are trying to establish a value for a gold alloy in a counterfeit you need to make some assumptions when calculating the range of actual value.

Alloying with copper has the added effect of altering the volume of the alloy (the technical reason I can not recall, but it does.) So if you assume copper as the only alloy and you use SG as an estimate of value you get a deviation that increases as the gold content decreases. If you presume silver or platimum is the only alloy you are likely to overstate the melt value. I normally estimate purchase values using the 100% copper alloy because it results in a "safer" value estimate. Actual assay costs for a mixed alloy run fairly high (in the 40% range for small objects) so I believe my offers are very fair.

When estimating for customers, I will typically forward a copy of Earle Calley's Study entitled "Validity of the Specific Gravity Method for the determination of the fineness of Gold Objects" Department of Chemistry, Ohio State University. I provide the observed SG and indicate the probable value using the Three assumptions in Caley - Silver only - copper only and equal proportions of copper and silver.

Here is a link to the entire paper - it is interesting reading but if you wade through it you can decide for yourself which alloy percentage is the fairest.

https://kb.osu.edu/dspace/bitstream...9N02_073.pdf

snowman - you can get into just about as much science as you can handle. I find any test fascinating. I have never had access to a mass spectrometer so I don't know how useful it would be. The XRF tests I have had done (back in New England) provided some great clues on both originals and counterfeits. The tests need to be interpreted properly and you need to know exactly where the test points were (surface of a clad layer or worn points for example). But once you can control exactly where the test is done - you can really learn a lot about the composition of the coin. An average reading like some XRFs do is of limited value since it randomly selects and averages 6 or 8 surface points, but the newest ones I saw can pick a precise (tiny spot) for the test. That way a worn coin can have both the surface coating and the core analysed.

I understand that the Colonial Coin Club in Boston now has access to an XRF apparatus as well. They brought one to a coin show a year or so back. But they got that AFTER I moved to NC. My access to an XRF was through a friend who worked in a lab with an XRF machine used for testing for metalic contaminants in filters. But he was injured and is not working anymore. In North Carolina, I have not yet located an XRF that I could get access to cheaply.

One of the most interesting facts I learned from XRF testing is that the original coins from certain mints contain trace contaminants that make authentication relatively easy because counterfeiters would never think to add them. There are always 5 or 6 surprising elements in the coin. Some like iron can come from ground contamination. The presence of zinc in an early coin is always suspicious because it boils off so easily and early mints used open crucibles. I normally make reference to only one of the trace contaminants because that one is now fairly well known. Mexican coins made before the 1860s at several mints associated with Northern silver mines (like Zacatecas) contain gold. As much as 2% by weight according to my tests of originals but never in my experience has there been less than 1/4 percent gold.

Of course most counterfeits can usually be spotted by what they don't contain. The XRF test works graet on cut or drilled coins because an analysis of the core is possible. You can also clean off a cut area without damaging the coin itself. That way you don't get confusion from patinas and surface contaminants.

Did you happen to notice the price for the first coin I listed? $260.55 - That is a good price for what I believe is a $30 silver forgery.