Mexico 8 Reales 1761

No problem to me so I agree it is real. Henry

I see nothing that makes me really suspicious.

I would however, always advise weighing and determining specific gravity. Your results should be about 26.4 to 26.8 grams and the density should be 10.31.

It should also contain roughly 2,000 ppm (0.02%) of gold at a bare minimum which is enough to register quite easily on a hand held XRF tester. See if a local coin dealer or jeweler has one.

One day coins collection would become science. Very ironic!

Bob,

I am working as a medical technologist in a public hospital. We always face a problem of accuracy of results and reproducibility of a test. Same argument would also happen in XRF and S.G., how accurate your test is?

I don't always resist scientific methods to confirm metallic contents in a coin but sometime it is obvious that a coin is fake or is genuine. Then the use of another method to confirm is an excuse to face a question. On the other hand, we are not sure in two hundreds' years ago, a mint or a mint master had a good faith to mint coins with absolute good enough silver used? Some coins of Croatia Ragusa crowns had S.G. as low as 10.0 are still genuine coins.

Scientific data is a reference to determine a coin is genuine or not but I still rely on the craft or skill of a coin minted. The experience of determining a coin is fake or not needed to be succeeded generation by generation. I am deeply impressed by the sentence in your book : Wally always believed in helping children and teens to develop their interest in coins because he knew they were the collectors of the future. Without new collectors numismatics will die.

I am always appreciated to those share their experience on numismatics unselfishly and would be willing to publish a book even though via the countless difficulties, like you.

I have also published my coin book in HK last year (nearly the same time as yours). My aim is to arouse coin collectors and history fans to know more about the importance of coin (actual silver coins in my book) in histories. The feedback is of course not better than yours.

Please forgive my grumblings.

Henry

Henry Test accuracy.

The XRF tests were done in three different labs. The most recent RTI used a new state of the art apparatus that can get accurate repeatable results to 10 ppm or 1 ppm depending on exposure time. Earlier tests were less precise based on the particular apparatus. But even the tests I did using a first generation lab XRF were accurate to the limits of the machine which in 1996 was about 1,000 ppm. I always used control coins like my 1805 Mo TH Class 2 which has now been tested 6 times. The earliest machines read no gold for that coin because they were not precise enough but this new machine found 12 ppm. That is the first time the coin has tested with a detectable level of gold. The 12 ppm is 0.0012% a very low level for Mexico City during the patio period.

For SG I use different scales. I have a cheap digital where I run tests in a few seconds. These will vary but not outside the limits I need. Almost every coin that I get I check with an Ohaus 4 beam 1/100th gram mechanical scale. Most counterfeit coins can be tested on that 1/100th gram scale because I am looking for SG expressed to three significant figures 10.3 or 10.2 or 10.1. When I am trying to get a more precise result I need to use a 1/1000th gram analytical scale. I use that scale on rather rare occasions because XRF is easier. The scale is getting old and I have been having some problems in set up. I think I need to buy a new one but they are not cheap.

Just like XRF testing with hand held guns - you can pick out the really bad coins - perhaps 98% need only a 1/100th scale or a hand held XRF - but on more difficult coins like Class 2 made before 1870 you need a 1 to 10 ppm XRF or a 1/1000th gram scale. So far I have not had many problems with repeat-ability of my tests.

Regarding debased coins made in the mint (frauds) I am open to the possibility they exist but I look for records to prove it. If no records exist documenting a coin as debased at the mint (unlike the 1828-1829 Ga or 1834-1836 Go or 1834 to 1835 Zs coins which were documented at the time) I become suspicious that the coin is counterfeit - a fraud that originated outside the mint. I have seen too many counterfeits passed off as debased when they were just plain counterfeit. They are also called test strikes or patterns but these labels are also given out too freely.

I think I have seen too many scams and have known too many forgers and counterfeiters to blame mint officials easily.

That at least one other example exists that's considered genuine and visually matches up well with the characteristics displayed by yours goes a long way toward validating your specimen.