Ferdinand VII 8 Reales - 1821 - Zacatecas. Or ... ?

Hum, I have to do my first SG test :)
Very busy right now, I'm back from vacation, and have to do all the work that have been waiting then ...
I'll come back here as soon as I've done that !

I just Googled and found that hand-held XRF analysers exist.

I wonder how much an entry level machine costs, and whether it's possible to hire them.

Is XRF = X-ray Fluorescence? I study a bit from an essay of Wikipedia, it is likely a tool to identify different kinds of chemical elements or compounds in any trace amount. How can it be used to identify the age of an old silver coin? Who can tell me more about the principle of this technique or suggest a link to a correct site for me? Thanks in advance.

Pertinax, I am happy to tell you how I can measure the S.G. of my coin. This is the method learned from swamperbob. The principle is based on Archimedes's law of buoyancy.

Hardwares (shown below):

1)An electronic scale with two decimal places
2)Distilled water
3)Two standards: 1797 2D cartwheel (0% Ag) and a .999 Sterling silver (100% Ag)







Data:
1)Weight of the hanger 1.72g
2)Weight of the iron wire 0.23 g

In air(A) Net wt(N) In H2O(W) A-W S.G. %Ag

100%Ag 33.11 31.16 30.12 2.99 10.46 100

0% Ag 57.0 55.05 50.79 6.21 8.88 0

My 1820 28.8 26.85 26.17 2.63 10.248 86.8

Calculations:

N = A - 1.95 1.95 = Weights of hanger + wire

SG = N/(A-W-0.01) Suppose the floating effect caused by
wire wound around the coin

For XRF tests to be useful they must disclose trace elements to the level of 10 or 20 parts per million. A tester that reads to 1% plus or minus is WORTHLESS for authentication.

The theory behind XRF testing is that there are elements in any coin that are "contaminants". A silver / copper alloy will contain far more than 2 elements when analysed. That is simple fact. But there are some elements that should or should not be present based on the origin of the silver and the methods employed in extracting and refining the silver. These factors change over time AND when forgers get involved they usually vary WIDELY.

While tests on specific coins still need a good deal of experienced interpretation there are elements always found in early 8Rs from Mexico that are missing in later made coins and those made in Spain or South America even in the same period.

What specifically all those trace elements are is not, nor should be public knowledge. Once published that data changes the playing-field and counterfeits made AFTER the data becomes well known - could be corrected.

At present there is one very common contaminant that is extremely well known to forgers and authenticators BOTH because of previous publication of data. That contaminant is GOLD. Silver mined anywhere that was extracted using the patio process and refined by cuppellation did not remove all the gold from the silver. Therefore to have been made in Mexico in say 1820 a silver coin MUST contain some gold. How much? I am not saying.

The study results that define the upper and lower limits of this range are at present being retained as proprietary data to protect the integrity of the process. If the forgers want to get the same information let them spend a few $100,000 and get it themselves.

Pertinax I think 50 would be a bare minimum unless you were planning to do just one very brief period at one mint. As I noted there is a range of variance seen even in coins of the same date from the same mint. The limit of the permissible range of variance is the most critical factor when you view several elements in relation to one another.

Also the apparatus to do the testing will run near $100k without training. As an alternative you can of course hire the testing to be done. A professional XRF test in a lab still runs near $50 for each test - it may come down with volume.

So even if your 30 tests was enough to establish the range accurately that would cost you $1500 just to discover a proper mix.

Then you would need to test each of your component metals to see what trace contaminants you get in each of them. By mixing "pure" silver and "pure" copper today you still end up with that digit AFTER the .999 fine which consists of impurities. Silver is 0.999 fine commercially - but you should do an XRF to see if it actually that close. That 0.001 is one ten thousandth or 10,000 millionths or 10,000 ppm. It could theoretically contain 50 different contaminant elements each at a density of 200 ppm or more. How many of those DO NOT belong in your mix and how do you get rid of them? That is a lot of area to hide a 10 ppm contaminant that does not belong. So getting the elements pure enough is a hurdle. Copper being less valuable is commensurately less pure.

In addition, remember that a typical original 8R has a list of anywhere from 7 to 12 contaminant elements (excluding the lighter elements like Aluminum). You might need to add one or two of those to any random batch. Where do you get pure Tungsten or Iridium or Cadmium and who can make a mix that contains only 50 ppm Cadmium anyway?

And on top of this you need to cast, roll, laminate, cut, adjust, edge, pickle and anneal your metal before you get to strike it. Each step has the threat of contamination which could void your work up to that point.

The technical issues of creating the perfect alloy from raw metals currently available is at present nearly insurmountable. That is why some specialists do advocate FULL RELEASE of test data.

But for now we are not to the point of release.

Of course, in doing the foregoing you would have missed a far cheaper solution.

Anyone care to hazard a guess?

That is the solution but for obvious reasons the target would of necessity be common date coins NOT the rare stuff and the margin is very low.

But isn't that the objective of authentication - to leave no place for the forgers to operate at huge profits?

The junk fakes that pass today cost as little as 1 cent to make and bring $30-50. That is what NEEDS TO GO.

Henry - Forgers are doing what they do for profit.

If the profit margin can be reduced there will be fewer forgers attracted to the business.

Now all we need is a cheap way to do just that.