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 Replies: 12 / Views: 5,083 |
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Valued Member
United States
84 Posts |
Hello,
Lemme start off by saying I'm a newb. I bought a proof set gold eagles and one of my coins is overweight.
My scale runs about 0.0015 toz on the heavy side, (using the calibration weights) and the coin (1/2 toz eagle) is 0.0050 +/- 0.0015.
How much variation exists in planchets from the US mint?
PS. Thanks in advance
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Pillar of the Community
 United States
5953 Posts |
An eagle contains 1ozt of gold but its only 91.67% Gold hence the coin weighing more then an ozt.
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Pillar of the Community
United States
3345 Posts |
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Pillar of the Community
United States
2120 Posts |
 Also, as a side note, ASE (silver eagles) are slightly over weight, even though they are .999 fine. IIRC this is to ensure they are never under 1 troy ounce. Topic about it - https://goccf.com/t/115394 |
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Valued Member
 United States
84 Posts |
It's supposed to be 0.5455 troy oz. I know the gold comp (silver, etc %) and its not silver.
So again: 0.5455 mine weighs 0.5490 troy oz. Thats 0.0050 over.
The 1oz, 1/4oz, 1/10oz are all balls on 0.0015 heavy (the calibration is off, all my calibration wights are 0.0015 over. Dont want to re-calibrate right now. Precision is all I need.
Thanks
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Pillar of the Community
United States
5953 Posts |
0.156 grams overweight is a little on the excessive side but It could be someting a simple a Cud in the reeding The Mint site does not list weight toloerances but states that the coin must contain the stated weight in gold. A little extra copper or silver in the allow would account fot the weight difference. A specific gravity check is about the only way you will know if the extra weight is gold or not. |
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Valued Member
United States
84 Posts |
yes, thank you. I had to do a double take at first when you said grams lol.
I remember 20 years ago in college, we used something called (hope I got this right) a pyncnometer. You drop the weighed object into a liquid (usually water) at the top was like a thermometer that read displacement to get SpGravity (density). I also remember a metal cup with a lid, but back then we had the really good analytical scales for the lab.
Yes I also think it's kinda weird that the US Mint doesn't specify any tolerances for public info other than the fact a 1oz eagle has AT LEAST 1oz guaranteed.
A coin dealer told me that weights do vary. I was concerned since I bought the set on an e-auction website.
Thanks in advance,
Tom
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Bedrock of the Community
United States
10982 Posts |
Quote:
It's supposed to be 0.5455 troy oz. I know the gold comp (silver, etc %) and its not silver.
So again: 0.5455 mine weighs 0.5490 troy oz. Thats 0.0050 over.
The 1oz, 1/4oz, 1/10oz are all balls on 0.0015 heavy (the calibration is off, all my calibration wights are 0.0015 over. Dont want to re-calibrate right now. Precision is all I need.
Thanks
We're talking about 1/10 of a gram so unless you've got a calibrated analytical balance, you're well within tolerance.  |
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Pillar of the Community
United States
2295 Posts |
Like others have said, they will be slightly overweight to make sure they contain a full troy ounce. |
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Pillar of the Community
United States
1027 Posts |
All US bullion coins (and because the numismatic versions are made from the same blanks, them as well) are guaranteed to contain the specified amount of PM. SAEs are to contain no less than 0.999 Toz silver and GAEs (and Buffalos) & PAEs are to contain no less that 1.000 Toz gold or platinum (and fractionals their respective amounts). Because of this guarantee, the nominal weight is above what might normally be expected so that the nominal minus the tolerance provides the proper amount of PM. Even your overweight coin is less than 1% high, which if we assume it is at the high end of the mint's tolerance means that the coins are nominally 0.5% high with +/- 0.5% tolerance, which is not unreasonable, IMO. I would assume that to at least some extent, the tolerances are set by the blank vendors. They of course want to keep tolerances tight so they don't waste too much PM but there comes a point where tightening the tolerance costs more than the PM saved by doing so. The blank vendors surely try to reject overweight specimens before they ship to the mint but the mint has no incentive to check anything other than minimum weight, a mildly heavy weight is probably not really an issue to the mint. Also it is quite possible that the mint tolerances are not symmetrical. They might use something like a nominal +0.3%, +0.7%, -0.3%.
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Valued Member
United States
84 Posts |
That all makes sense until we get into error analysis(dont want to go off-topic here) but I do know the government posts specs for any manufacturer/vendor must meet. I used to work in industrial adhesives with government and I think we worked of ASTM (material)specs. Forget alot of that stuff now, but I do think they publish that to a potential contractor that makes the blanks. Whether it's classified or not, idk.
But I do understand what everyone is saying where it is desirable to be OVER some to insure they're not under.
There was a show saw once before "Secrets of the US Mint", think it's on the History channel or something. I saw it on the guide last night and DVR'd it before I went to sleep.
I think the reasons I was concerned is because I am a newb buying on auction and what I remeber on that show. They had the gold bars (on one side)on a huge balance (counterweights other side) and the guy threw a dollar bill on the scale and it moved. When I saw that I thought "there is no way their measurements are that good!"
Now, the place I think makes the blanks is in Rhode Island I think. What their tolerances are, idk. And then the blanks go to West Point (which explains why my car was searched 5 years ago when I went there, didn't know the mint was there lol) I'll make some time later tonight to watch the show.
So being a newb I didn't want any counterfeits to pass me. I looked for seams on the side and I kinda thought the staff on the obverse St Gaudens was too close to the rays. Even the 1/10 oz showed some seperation. I've been on heightened alertness since and still have another day or 2 to return, but already gold is past the melt value of what I bought this set for ($3050 USD)
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Valued Member
United States
84 Posts |
I just wanted to do a follow up on this dead thread because I think it is important for someone in the future to know. If you ever wondered if a gold coin can be overweight without being a counterfeit.
Apparently it can be overweight. I received my graded coins from PCGS and they gave it a generous PR67. They have scanners that can check for composition in a non-destructive manner. The previous owner had taken a scratch sample for testing, so a 67 grade was better than just a "genuine" grade.
Like I said, it may be useful for someone in the future. Previously I searched all kinds of combination words to see if someone had a circumstance like mine. I found some that never had a follow up, and some skirted the details. I think some comments to this thread were retracted after comments like I was an idiot to buy this, and some were dead sure the coin was fake.
Is it proof positive? Maybe it just got by PCGS if it's not, it's a good fake. Thanks for everyone who helped.
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Bedrock of the Community
United States
12437 Posts |
Keep in mind that gold is an extremely dense metal so it is quite difficult to replace it with another metal yet still match the physical specs of a coin. Tungsten is the only practical substitute for gold but it is an incredibly hard metal that is virtually impossible to strike into a passable coin. Usage of any other metal would cause an increase in the size of the coin to maintain the weight or result in an markedly underweight coin. However, the big worry with tungsten is the possibility of tungsten-core gold bars.
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Replies: 12 / Views: 5,083 |
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Posted 06/05/2012 4:21 pm
