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 Replies: 8 / Views: 1,428 |
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Valued Member
Canada
367 Posts |
I recently purchased a 2-oz gold coin on ebay. This proof coin, Sower Euro's 10th anniversary, was made by Paris Mint in 2012. It has a face value of 250€ and a mintage of 500. Before this purchase, I have collected Canadian coins exclusively. When I received the coin, I was surprised by the red spots on both front and obverse sides. I was wondering if this a real 99.9% gold coin. Because I never saw these kinds of red spots on my Canadian gold coins, which usually have a purity of 99.99% or 99.999%. Then I did some research online. It seems red spots may appear on gold coins, especially old ones with copper content. I'd like to hear your opinions. What do you think of this coin? I'm attaching a few pictures here.     |
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Bedrock of the Community
Australia
21788 Posts |
To my eye, the artwork of Roty clashes with the modern artwork of the rest of the coin. That is just me, and so this comment can be ignored. I note the spots. Need more information: What is the purity (fineness) of this piece? Lower fineness (perhaps 500 fine?) may have some bearing on this inquiry. I suspect there may have been some debris (oil droplets?), on the surfaces before it was encapsulated. Can the capsule be opened? -an acetone dip may help. If the capsule is press closed rather than screw closed, (like openable Royal Mint capsules), you will need to be very careful to prize it it open without damage. |
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Valued Member
 Canada
367 Posts |
Hi sel_69l, thanks for your comment. The coin is 99.9% gold. Below is the official product page for this coin: https://www.monnaiedeparis.fr/en/sh...2-oz-be-2012The capsule can be easily opened. In fact, I took the first two photos without the capsule cover. I already tried to use a soft towel to clean the red spots, they can't be removed. It seems the red spots developed by themselves. |
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Bedrock of the Community
Australia
21788 Posts |
At 999/1000 fine, those spots cannot be the result of minor inorganic corrosion.
To my way of thinking therefore, I am thinking organic deposits, and so should likely removed with acetone. Give the coin a good soak in a acetone over a 24 hour period, in sealed jar, and see what happens.
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Pillar of the Community
 United States
7953 Posts |
@YesOrNo, As you say, apparently this effect is well-known and doesn't relate to authenticity. There has actually been chemical analysis of these spots on other modern 99.9% gold euro coins, and the composition was mostly silver and sulfur, with smaller amounts of copper: http://projects.itn.pt/Corregidor/18.pdf Remember that a 99.9% coin may have 10 times higher concentration of impurities than at 99.99%, and 100 times higher than at 99.999%. This might explain why you are not seeing this on higher purity gold coins. If the listing is the one I see in an ebay sold items search, the seller used a stock photo and didn't disclose the spots, so you certainly can send the coin back. Edited by tdziemia
01/21/2019 11:31 am
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Valued Member
Canada
367 Posts |
@acetone thanks for the acetone tip. However, I don't have acetone right now. Would Isopropyl alcohol (Rubbing alcohol) work?
@tdziemia The paper was really interesting. I think it explains the spots on this coin. Do you know if the spots can still be easily cleaned?
I bought this coin at 3,700 CAD (or 2,780 USD), which is close to the bullion value of 2 oz gold. Therefore, even with these defects, I will keep this coin. In the worse case, I can sell it at the bullion value, I think.
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Pillar of the Community
United States
7953 Posts |
The paper is unclear about the ability to remove the spots.
For a different kind of spot, which the authors believe to be a result of the process to produce blanks for the proofs, they mention the ability to remove them with isopropyl alcohol. So I don't think it can hurt to try this (I would use a swab/ Qtip). But if these spots are silver sulfide, I doubt it will help.
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Pillar of the Community
Austria
566 Posts |
NGC conservation service will remove the spots!
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Pillar of the Community
United States
7953 Posts |
Is that humor, or a bona fide approach to improve the appearance?
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Replies: 8 / Views: 1,428 |
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Posted 01/20/2019 8:59 pm
