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 Replies: 24 / Views: 6,081 |
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Pillar of the Community
France
1591 Posts |
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Pillar of the Community
 France
1591 Posts |
I did a quick set of picture when I received that one.
I have to check that out with a lens, but the hole doesn't look like filled with coper.
There are strange colors in some places, at the edge for example.
Regarding this edge, it is interesting : it looks like a ribbon between two rails.
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Pillar of the Community
France
1591 Posts |
Swamperbob : I rechecked the whole coin with a nice lens, and didn't saw anything particular. The hole is made of silver, I don't see any copper there.
And the coloring is just the coin's natural color, some oxidation or dirt.
Shall I inspect something particular ?
Thanks for your help :)
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Pillar of the Community
Hong Kong
1270 Posts |
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Pillar of the Community
France
1591 Posts |
I don't have the coin on hand right now - I'll do my first SG test on it then :)
Swamperbob : I was mentioning that one. From the features on that coin, which details seems off to you ?
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Pillar of the Community
France
1591 Posts |
Bump - for Swamperbob :) Thanks in advance !
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Pillar of the Community
United Kingdom
2133 Posts |
The silver fineness for these coins is listed as 90.3% silver.
What is the specific gravity of this fineness ?
For that matter, what is the specific gravity of sterling silver ?
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Pillar of the Community
United Kingdom
2133 Posts |
What is the weight in grams, please ?
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Pillar of the Community
Hong Kong
1270 Posts |
My 1820 piece:
weight : 26.85 grams
I did the S.G. of this coin on Aug 3:
S.G. of this coin = 10.248, corresponding to 86.8% fineness of Ag in my system.
S.G. of Sterling silver in my measurement: 10.46
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Pillar of the Community
United Kingdom
2133 Posts |
The weight is a bit under the listed weight of 27.07 grams but well within the norm.
Depending on the accuracy of the equipment, I think the measurement of the SG is also OK.
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Pillar of the Community
France
1591 Posts |
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 !
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Pillar of the Community
United States
5362 Posts |
Interesting coin - I guess I missed this thread. Busy on book.
SG is a great test and definitely is definitive if done with accuracy. There are a lot of cheap scales that read out to 1/1000 ths but which are no where near that accurate. I have tried digital and it is quicker but not as accurate as the big old analytical balance. A 4 or 5 beam mechanical balance is of course better (but expensive) and it takes time to get it right. Digital is great when you suspect GS or CN or some bronze alloy. But when dealing with high grade debased silver not so great.
Full weight silver counterfeits CAN and DO EXIST. SG can detect 95% or more of frauds using an incorrect metal content. But SG can not detect all frauds. A counterfeit can be made using an alloy created to match the density of 903 fine silver (10.31) and a counterfeit can of course be made using 903 fine silver.
XRF combined with the surface characteristics of the coin itself are then the best tools available.
But always keep in mind that the better forgers all know this and can answer most forgery tests with improved techniques. But they are somewhat limited they still must find a buyer that is uninformed - and the more expensive the coin - the fewer "uniformed collectors" there are.
It is easy to find a sucker for a $7 fake but much harder to find a buyer for a fake that costs $700 to make.
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Pillar of the Community
United Kingdom
2133 Posts |
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.
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Pillar of the Community
United States
5362 Posts |
Those are the junk yard types and the ones used for field analysis of pollutants - don't think they would be great for distinguishing much more than SG can for a fraction of the cost.
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Pillar of the Community
Hong Kong
1270 Posts |
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.
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Pillar of the Community
United Kingdom
2133 Posts |
wonghinghi,
What method/caculation did you use to calculate the SG for your coin, please ?
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Replies: 24 / Views: 6,081 |
Posted 08/13/2012 02:40 am
