1789 8 Reales

I see the XRF results - they are done to 100 ppm level.

At that accuracy level both Gold and Platinum as a minimum should have been present. All Mexican refined silver processed before the 1870s has gold in it.

Also several other trace elements.

I have never seen a test this clean indicating no light metals or organics except for recently produced forgeries.

John is part of the discussion by default because he ran all the tests in the book and his the a co-author.

Swamperbob,

now seriously:




Do you believe, that this coin might be a recent forgery?

This would be indeed shocking, but I would not even nearly consider it.

If the XRF test results are correct the coin was made AFTER 1870 at the earliest.

I have two coins that I wonder if you believe are genuine or not. Both coin show surface silver concentrations in the 91% range using XRF primary alloy is copper in both cases about 8%. One has a Specific Gravity of 10.31 and the other 9.97.

What do you think of this one? It has been tested with XRF. The weight is 26.95 grams. Is it genuine?




Or this one also tested with XRF is it genuine? weight is 26.9 grams.

Hi John. You say




The issue goes well past XRF alone. The other scientific methods which include SG and the geometry of the edger are both violated by this coin.

I fear your quote above will be interpreted as support for his position that science including XRF can be ignored in favor of opinions that the coin looks good therefore it is.

I completely agree with you that an XRF test (done accurately with a decent instrument like you used) is a definitive test for the age of the silver, If a valid test shows no Au or PT it proves beyond any doubt that the coin is a very recent forgery (1878 if US origin silver or 1900 for Mexico origin depending on the date that the cyanide process was introduced at the refinery).

Au and Pt in the alloy proves only that old silver was used. The correct ratio is seen on numerous Class 1 contemporary counterfeits made with Sheffield silver plate.

I agree the test apparatus used was inadequate. That was obvious from the print out - the results added up to 100% which our tests have never done and no trace contaminants were noted at all. There are always missing non-metallic traces or light metals that do not appear like Aluminum.

But in addition to XRF - I have SG results on three coins made using the same reverse die punches that produce low SGs. The coin posted by Henry which also matches the coinworldtv coin by die type also shows a low SG 10.195. That is 810-840 fine silver - that is a Class 2 coin by definition. My coins fall into the 80-85% range as well. So 4 of 5 coins with known SG are deficient, This looks like a Class 2 type made between 1830 and 1840 and not much later. Tests done by British authorities show higher silver contents in the restrikes by the 1840s.

Since there are no Genuine Portrait 8Rs made at the Mexico City mint that test 81-84% fine silver (proven by mint reports from the period - US, GB and China). SG then becomes a definitive scientific test for forgery.

In addition the use of a correct edger based on geometry requires 2 overlaps that are opposite one another and of the same length. The specimen photographed by Henry has an identical JOIN of two adjacent circles instead of an overlap in design and the laps are on Henry's coin are NOT exactly opposite one another - they are 5 degrees off.

What we have been arguing over is the validity of tests based on science - physics for the SG and XRF and geometry for the edger. Failure to meet any of the definitive scientific tests proves that the coin is a counterfeit.

I do not want Filip latching onto your first statement and making the interpret that the case is actually still in doubt. I have zero doubt about the status of this coin in Class 2.

Just one last thought remember the L. Beck paper that with time and proper environmental conditions silver coins WILL show elevated Ag levels due to copper leaching and silver migration between the inner/outer cores. We have seen many examples of Class 1 & Class 2 with Ag levels above 92%. But this is coin dependent. I was doing some other research at EDAX and for a 1964 Kennedy half (only one example) no Ag migration occured after the coin was cut in half and the inner/outer core SEM/EDS results were recorded. Still one coin but it appears this L. Beck silver enrichment research takes TIME on a silver coin as with these early 8 Reales.

JPL

No answer yet on the two coins I posted? No one cares to risk a guess?

Henry - Regarding the edge being out of alignment - I personally do see that as proof of the coin being a Class 2 counterfeit - but a very early one made before the Schroffs in China started using SG testing. Your SG results of the Keyhole/porthole window variety 10.195 essentially match the three I have which tested in the 80-85% range.

This early type of Class 2 silver restrikes were only made briefly between 1830 and 1836 or thereabouts. SG was first demonstrated to the Chinese by the British in 1835.

Thereafter the assay went up to nearer correct. \\I see little if any difference in actual value between the earliest silver restrikes and genuine issues. Rarity is comparable.

The pictures I have are all I have right now at home and the coins are in the Bank. But for purposes here you may presume BOTH have decent looking circle and rectangle edges that have overlaps of equal length at 180 degrees. I recall one does for sure and for the other one I am fairly sure it does but have not seen the coin for at least a year.

This is an exercise in die design - all you need are the two pictures.