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 Replies: 7 / Views: 3,672 |
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Valued Member
United States
55 Posts |
I recently acquired a couple gold eagles to add to the collection, a 1979-S that looks like it might have been in a bezel (center is worn to G, but rim/denticles look AU) the other is a 1892 AU/BU. I was checking them out to make sure I didn't get sold some fakes (trust, but verify). I cannot find how thick these are supposed to be anywhere. Red Book only lists diameter and weight, and after much googling, I am coming up short. The 79-S is 16.42g, 27.2mm diam and 1.9mm thick at the rim The 92 is 16.71g, 26.96mm diam and 2mm thick at the rim Does this sounds about right on the thickness? Thanks! |
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Bedrock of the Community
Australia
21788 Posts |
The problem that I have is that I do not understand how the thickness of a coin is measured.
I can calculate it from the known density of the alloy, the mass and the diameter, but that will only give the average thickness. Many coins have at least slightly dished fields to allow for the relief in the center of the coin. As mentioned above, the rim thickness can be measured.
I will therefore consider myself dumb on this matter, until some friendly soul on the CCF can enlighten me.
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Bedrock of the Community
United States
10982 Posts |
I measure at the rim. 2.0mm is pretty darn close. I don't know the exact thickness but $10 classic gold eagles are very close in size to modern $25 GAE and they're 2.15mm thick. The $25 GAE has slightly more gold in it but is a good reference point.
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Valued Member
 United States
55 Posts |
Thanks both. The modern 1/2 ounce GAE is probably a close enough comparison as far as dimensions.
Also, obviously I meant the first one is an 1879-S, I just noticed my typo!
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Pillar of the Community
United States
3546 Posts |
This subject has always intrigued me because of the apparent scarcity of consistently available thickness information from verified reliable sources. With this being said I would like to know what you folks feel about the accuracy of the following thickness info. for the US coins taken from the following URL: http://www.onlygold.com/TutorialPag...nVersion.htmAnother question I have on this particular URL source is if the printed thicknesses are the maximum thicknesses of the US gold coins considering the thickest areas measured for the highest relief points of the coin. I also would assume that devices like http://www.fisch.co.za/operation.htm would have to be manufactured to allow the thickest point of the coin to pass through or risk not allowing a genuine minimally worn coin pass through the test slot. Any thoughts on these points would be helpful. |
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Bedrock of the Community
Australia
21788 Posts |
mdpmedia: I did the calculation using the Australian 1oz. Lunar gold coin calculating for nominal thickness. The chart reveals a thickness for this coin as 2.65 mm. Using a radius 1/2 of 32.10 mm equals .1605 cm and a specific gravity for gold at 19.32 g/cc, I calculate the thickness at 1.99mm for this coin.
It seems that from the above that the quoted thickness of 2.65 mm is most probably a rim thickness, not an average thickness as I have calculated.
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Bedrock of the Community
United States
17884 Posts |
The reason you don't see any figures for thickness is because you can calculate a thickness for what the blank would be, the the actual thickness of th finished coin is a function of the strength of the strike.
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Valued Member
United States
55 Posts |
Conder101: Gotcha, as long as it's not ridiculous (like two times "normal"), it's not the main factor.
Now thinking about the diameter on the 1879-S. Is 27.2mm out of tolerance? I guess it's only .7%. Is that within spec?
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Replies: 7 / Views: 3,672 |
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Posted 10/23/2010 8:54 pm
