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 Replies: 9 / Views: 1,360 |
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Pillar of the Community
United States
2120 Posts |
Hi Everyone. So There is a coin I'm considering buying from my local dealer. He was gracious enough, given my concerns, to allow me to take this home to photograph and research it before buying. I believe this coin may be a contemporary counterfeit based on a few points; See pictures at the bottom. There are low res (embedded) and Hi-res (link above photo) for Front / Back and then a few angles of the text and edge. 1. Weight/Composition: I know that QC in this period wasn't always the greatest, but I don't expect it to be as far off as it is. The following was the average of three readings from an XRF machine. I also want to say I read SwamperBob say somewhere that there should be some trace amounts of Pt, but I don't remember if that applies for Hermosillo. Ag: 95.946% Cu: 3.716% Pb: 0.316% Weight: 26.6g 2. It's a little hard to tell, but it appears to me that the 0 beneath the 1 in the over day is at an odd angle. If it should be oriented at 12 O'clock, it looks to me like its oriented at 10 O'clock. However with all the other apparent doubling (around the mint mark) it might be correct. I couldn't find a good picture of an 1870 Ho to verify the 0's orientation. 3. The eye on the eagle looks like a smushed doughnut with a slit in the center. Almost like someone punched this poor bird in the face before it modeled.  However, I have seen this look on many others from Hermosillo around the period. Thanks for any and all help on this! Hi-Res Version: http://i.imgur.com/dpVHPmE.jpg Hi-Res Version: http://i.imgur.com/Ke4rgPb.jpg |
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Pillar of the Community
United States
5362 Posts |
Based on appearance the coin looks pretty good to me. The overdate looks exactly like the photograph in Resplandores.
Even the recut 0 in the assay legend is present. So the coin is either real or a very exceptional cast copy.
The weight appears to be slightly low for an issue that was used primarily as an export coin. The coin is 98.4% of standard. Making allowance for wear, I believe that you get a low but completely legal weight. Based on comments in period works - low weight coins were often used as payment for workers - they were not exported to banks or sold as export coins. So I could discount the weight as not that critical. The coin may have remained in Mexico.
So the only issue as I see it is the XRF results that show high silver, low copper, high lead and no Platinum or gold.
The test results for silver typically show some amount of surface enrichment. Based on what I have read there are two causes. First strike enrichment which causes silver to flow to the surface and can add a couple percent to the reading. The second cause is surface depletion of copper through surface erosion. Copper being more reactive than silver tends to deplete. But I do not see any evidence of corrosion.
The lead present in the coin is quite high. We do know that lead is used in casting to improve the quality of the cast and so when readings are this high some suspicion can result. It must be noted that native copper deposits do include lead so the presence is NOT out of the question.
The test results for the Gold/Platinum ratio used in the book are based for the most part on Mexico City Portrait coins, but the results extend to the provincial mints as well. Our results were also taken with a very sensitive XRF apparatus.
So I need to ask what apparatus was used to evaluate the coin and how small a trace contaminant could be read? Also was the apparatus calibrated for gold and platinum?
At this point, I think the chance of a contemporary forgery is not high.
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Pillar of the Community
 United States
2120 Posts |
Thank you for the very concise response Bob!!
Ill find out about the Model of the XRF machine and how its calibrated.
The lack of other trace PMs concerned me too. ( I remembered you saying it before).
Thanks again.
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Pillar of the Community
United States
2120 Posts |
It's a Niton XL2 http://www.niton.com/docs/literatur...ec_Sheet.pdfIt wasn't ever specifically calibrated, so that would probably account for the lack of trace elements and varying results from the 3 readings I took. Largest spread on silver was 1.1%. I think given all that, and your analysis, I would concur that it is most likely authentic. Thank you again! |
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Pillar of the Community
United States
2120 Posts |
Ended up purchasing it for $90.
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Valued Member
Germany
194 Posts |
I say it was the right decision - and a good buy :-) !
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Pillar of the Community
United States
2120 Posts |
Yes. I am pretty happy with it.  |
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Pillar of the Community
United States
1962 Posts |
Forest through trees... if nothing else, step back and look at the surfaces/toning on the coin. Beyond that, everything is typical for Hermosillo of this time.
How are the surfaces underneath that tone... original or old cleaning? Either way, $90 is a good price with that much meat to it... I don't think a lot of local dealer types have caught on to the fact that Cap & Rays have thoroughly shifted in price in recent years.
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Pillar of the Community
United States
2120 Posts |
I don't see any obvious signs of an old cleaning but likely it was. The color is much more dark and bluish than a "re-tone" usually is.
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Pillar of the Community
United States
2120 Posts |
Just sharing a close up of the over date with the new microscope I got today. Not bad for $30  Edited by Namachieli
08/22/2013 10:28 pm
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Replies: 9 / Views: 1,360 |
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Posted 08/15/2013 2:04 pm
