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Opinions needed on weight of 1oz Gold Eagle
RedstoneCoins
Posts: 217 ✭✭✭
Many of you are familiar with my eBay case involving the 1oz Gold Eagle.
I took it out to weigh it, given the issues I had with the Seller, and I have discovered it weighs 34.08 grams.
The weight of a Gold Eagle is supposed to be 33.93 grams. This is 0.15 grams over, or 100.44% of normal weight.
Is this within tolerance, or suspicious?
I have not checked for specific gravity via the distilled water submersion test, though that is an option.
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Just a question... is there dirt or other residues on the coin? You might give it an acetone bath and hot water rinse and weigh it again. Cheers, RickO
You are also assuming that your scale is the alpha and the omega.
put a known good gold eagle on your scale to check your scale.
"When the rule of law collapses, civilization can no longer survive." - Martin Armstrong
Is your scale in Troy ounces?
Gold coins are required by law to contain the full weight of gold, so it wouldn't be surprising to find that some could be a fraction over as the cost to manufacture blanks will increase as the weight tolerance decreases and will eventually reach a point where it's cheaper to include a tiny bit extra metal than to attempt to prevent including it. Found this elsewhere- it's about Canadian Maple Leafs. but possibly still relevant:
"Surprised at the weight of gold Maple Leaf's, all 15 pieces weighed exactly 31.24 grams. Knowing that 1 ounce = 31.10 grams!"
"There is a tolerance level. The weight will NEVER be below 31.10grams but it can have up to 0.5% (There greater the weight, the lesser the tolerance). 31.24gram is well within the 0.5%."
There's no need to bluster about what I assume. I didn't say my scale was perfect. It has an accuracy of +/- 0.01 grams, which is standard for fine weights.
I weighed the coin several times, I also calibrated the scale against other objects that have a known weight. The scale is not wrong. The coin weighs 34.08 grams +/- 0.01 grams.
Thank you for the reference to another person's gold coin experience. Although the Canadian Mint is not the U.S. Mint, both are government mints and (assuming this person's coins weren't fake and were bought from a reputable dealer), the variations in weight should at least be consistent if they are going to be over.
I remember buying Silver Eagles from dealers that consistently weighed 31.3 or 31.4 grams. This alarmed me at first, knowing one troy ounce is 31.1 grams, but when the coins were subjected to a full scientific XRF test, and a distilled water submersion test for specific gravity, every coin was real. The government just made them a tad heavy using slightly thicker planchets.
I wasn't sure if Gold was treated to a higher standard, given the higher value. Hence my question.
Thanks for the data points. Useful in reference.
I have four electronic scales, and they will yield four different weights for the same coin.
Billy Shakespeare wrote a play about this.
My scale is capable of measuring in troy ounces, grams, grains, AVDP ounces, etc.
The weights given above are in grams for resolution purposes. It's easier to contrast 34.08 to 33.93 grams than it is 1.096 troy ounces over 1.091.
Try an XRF or a Sygma tester. I only trust scales so much.
Good question.
I don't see any residue. Though a bath in chemicals I'm not too familiar with would scare me, considering that it is a proof coin and I'm not sure how those chemicals would affect the surface.
I would have to do research on the effects acetone has on gold proof coins prior to considering that.
Thanks for the idea though.
You either have four inaccurate scales, or at best one accurate scale and three other inaccurate scales, considering that all four are giving you different weights.
I own more than one scale. It is very, very rare that I get different results from the same sample on each scale, and usually the cause is my own hand accidentally touching the scale, or wind (from a fan pointing downward), or my own breath adding kinetic energy to the plate of the scale, etc.
Sounds like you need to calibrate your scales.
I have the Sigma Metalytics.
Without going into too much detail, knowing what it tests for, and the depth it tests at, leads me to believe that there are ways to fool it if someone wanted to, or happened to make a fake that could pass within the tolerances of the machine.
It does pass the Sigma test, I will note. Though I would rather be too skeptical than too trusting.
I can't decide, so will go with all three of these:
Measure for measure
Comedy of errors
Much ado about nothing?
National Commemorative Medals of the U.S. Mint:
https://www.pcgs.com/setregistry/u-s-coins/medals-tokens/national-commemorative-medals-united-states-mint-1940-present/alltimeset/195526
so, you haven't compared it to a similar coin using the same scale?
I would trust the Sigma on this one. Further tests will confirm this.
"When the rule of law collapses, civilization can no longer survive." - Martin Armstrong
Given the pics you posted in the other thread, it looks like a good AGE to me. If its fake it is an unbelievably good one.
Collector, occasional seller
The OP seems to have had (or still does?) at least a seed of a doubt about authenticity. I hope it was one heck of a bargain.
Peace of mind is worth something.
If I had to pop a proof coin out of its capsule, weight it and consider dunking it in water for a specific gravity test then I might need to think about only buying from trusted sources.
There are so many fakes out there.
I bought coins from a dealer (brick and mortar shop nearby), and even he sold me fakes which he claimed he didn't know were fake.
Given that many fakes now contain some real precious metals, or an incredibly thick plating, and counterfeiters make their money on the margins, I am going to be more cautious about what I trust, regardless of the source.
They fake graded coins, they fake everything. It really pisses me off. Probably pisses PCGS off too!
So excuse my cautious nature. I test everything, regardless of the source.
Might be easier to make your own ingots/rounds then you will definitely know the purity.
@RedstoneCoins....Acetone will not harm any metal...it is an organic solvent, and will only remove organic materials. Perfectly safe for coins. Cheers, RickO
The mint tests the planchets. Surprised that the mint accepted and used them. Must have been in dire need at the time. Did anyone ever check with the mint QC folks about it?
So, how much over the mint's specs is this one ? I haven't seen the planchet tolerance given yet, or did I miss it somehow. could be a little heavy on copper, and not gold. I gave up trying to find the specs on the mints site. They cannot be produced under the specified weights, so with it containing gold, silver, and copper, I would say they can make them a little over in each metal, (copper more so than the others) but not under at all. Most likely just a heavy Planchet if all else looks correct, it is probably good. Not positively though, you would need trustworthy authentication to tell beyond a doubt.
I may not know what I'm doing most of the time, but I'm Damn good at it. 😇 😈
I know nothing about how to determine a real Gold eagle.
Years ago I bought 20 unslabbed gold eagles from a seller who later on proved to be questionable.
To alleviate my concern I bit the bullet, paid the grading co the fee and sent 4 coins (free with membership) in for grading.
They slabbed ok. One actually came back an MS67 so I was wondering if the grading co thought , "who would send in this coin"? From my point of view it was a great grade.
There is a minimum weight but no over spec- just the requirement to contain the full weight in gold. It would seem obvious the target would be to not be over weight any more than is necessary in order to insure that none are under weight.
Let's not forget this is a 1986, the first year of the series. I don't know if that means anything really but I would think they probably didn't have all the kinks worked out yet.
(grabbing the pics from your other post)
There does seem to be some sort of... "shmoo" on it. Maybe once that's off it will weigh a little closer.
Collector, occasional seller
That was part of my consideration. The Mint in the 1980's notoriously had lower quality control than today. That's why you can't find many MS70's of certain Roman Numeral dates, but can find many modern MS70 Gold Eagles nowadays.
Also, among the many Silver Eagles I've bought from dealers, the weights seem to be more consistent among newer coins, but the 1980's dates all seemed the be 31.3 to 31.4 grams. All passed XRF, Sigma Metalytics, specific gravity, etc. Just thicker planchets.
All right everyone, thanks for your input. I'm a natural skeptic. Thanks for assuaging my concerns.
but don't put it in a styrofoam or certain types of plastic cup.
"When the rule of law collapses, civilization can no longer survive." - Martin Armstrong
Did you measure the coin's specific gravity?
Edited to add ... and measure the diameter and thickness?
See http://www.doubledimes.com for a free online reference for US twenty-cent pieces
The previously pictured coin is an authentic $50 American Gold Eagle proof as is the unique US mint capsule.
"When the rule of law collapses, civilization can no longer survive." - Martin Armstrong
.
.
What happened to all your calculations?
Drill a hole through it and make sure it’s solid Gold
Www.killermarbles.com
Www.suncitycoin.com
You could also bend it if it’s tungsten it won’t bend
Www.killermarbles.com
Www.suncitycoin.com
Something does not sound right. Please weigh a coin and post the 4 results and the tolerance.
I have found that the last numeral after the decimal point may vary too much. A balance that weighs to the thousandth of a gram is really very accurate to the hundredth. I'll also bet than neither of you has diminished the effects of vibration and air currents where your balance is.
The ANACS lab in DC had a Sartorius balance on a very large granite block bench that was accurate to .001 +/- something. When they left DC for CO, the INS Authentication Bureau (first TPGS in the US) bought a Mettler balance accurate to .0001 +/- something to get better specific gravity results and added precision!
@ChrisH821 said: "...There does seem to be some sort of... "shmoo" on it. Maybe once that's off it will weigh a little closer."
Chris, there is not enough "shmoo" on that coin to even register on an accurate balance.
But all they do is look at it. But you can see a lot just by looking they say.
I tried to edit it but I got some kind of an error message, so I reposted them.
Then another error message. I'm hoping this one doesn't do the same.
maybe the error message was for your scale.
"When the rule of law collapses, civilization can no longer survive." - Martin Armstrong
When I began to research the specific gravity of an American Gold Eagle, I realized I had to determine what the theoretical specific gravity of the coin should be first prior to testing the one I have in hand.
So I took a look at the pamphlet included with the proof coin, and found that the Mint conveniently stated the exact composition of the coin's alloy in grams rather than percentages:
According to the pamphlet from the U.S. Mint, this coin should contain:
31.1 grams of pure Gold
Approximately 1.02 grams of pure Silver
Appoximately 1.81 grams of pure Copper
I decided to round after the 2nd decimal, given that the accuracy of my scale does not exceed +/- 0.01 grams anyway. This makes the math for calculating the theoretical specific gravity easier as it would be a foolhardy endeavor to compute the volume of space that each constituent component should occupy, but that will come later.
You will note that this cumulative composition adds up to 33.93 grams, rather than the stated mass of 33.931 grams the coin should be, according to the U.S. Mint pamphlet included with the coin. That is 99.997% of the theoretical mass of the coin, which is of acceptable accuracy for our purposes.
Now, to compute the volume of space each constituent component should occupy:
Gold has a specific gravity of 19.3 grams per cubic centimeter.
Silver has a specific gravity of 10.5 grams per cubic centimeter (rounded up from 10.49).
Copper has a specific gravity of 8.96 grams per cubic centimeter, though this metal has a varying SG based on the scientific source you quote.
That means the Gold in the coin should occupy a total volume of space of 31.1/19.3 = 1.611 cubic centimeters of Gold.
The Silver should occupy 0.1 cubic centimeters of space, based on 1.02/10.5 = 0.0.97 CC's (again, rounding by 2nd decimal).
The Copper should occupy 0.20 cubic centimeters of space, based on 1.81/8.96 = 0.202 CC's.
Which means the theoretical volume of the coin should be approximately 1.61+0.1+0.20 = 1.91 cubic centimeters of space. Based on our respectively derived calculation of the sum of the components' masses at 33.93 grams, that means the 1oz American Gold Eagle coin here should have a theoretical specific gravity of 33.93/1.91 = 17.76 g/cc. How patriotic! Maybe the mint planned this deliberately? Then again my math is the result of rounding by the 2nd decimal, the precise math could vary. But onwards. . .
Distilled water has an exact specific gravity of 1 gram per cubic centimeter. The theory behind water submersion/specific gravity tests is that, if you were submerge a coin in water (WITHOUT LETTING IT TOUCH THE BOTTOM OF THE CONTAINER - IT MUST BE SUSPENDED IN THE WATER FOR THE TEST TO BE ACCURATE; IT MUST ALSO NOT BE SUSPENDED BY ANY OBJECT THAT OCCUPIES A VOLUME OF SPACE WHICH EXCEEDS THE TOLERANCES FOR ERROR) that it would displace exactly one cubic centimeter of space of water for every cubic centimeter of space of coin which is submerged (and suspended) within it, which would consequently add one gram of weight to the scale for every cubic centimeter of water displaced. This assumes, as stated before, that the water is distilled and that the coin does not touch the bottom of the water container. To suspend the coin in the water without adding more volume to the scale is the tricky part. That's why a margin of error is necessary, because unless there's some massless/volumeless object which could hold the coin (magnetic suspension, perhaps? Then again, that might interfere with the scale), the strings or whatever you use to hold the coin will displace water as well. That's why it's important to use as little as possible material while suspending the coin. Anything else present in the water will interfere with the accuracy of the test.
But this is where a slight problem in the theory behind the tests' accuracy arises. Three small issues, really:
1) In practicality, when you submerge any object in water, microscopic bubbles on the bottom or side of the object (for a concave coin, or the reeds, or any high-relief coin, this issue would be particularly pronounced), the coin would have to be spritzed with distilled water first before submersion to minimize microscopic bubbles from adding to the perceived volume of the coin the bubbles' presence would create.
2) The volume of this coin is only theoretical and based on specific gravity for alloys by other scientific labs which may vary slightly, just enough, from one composition to another, based on who made it and under what circumstance, to where the actual specific gravity may be different.
3) When you calculate the theoretical volume by taking the constituent components' mass and working in reverse from their respective specific gravity, this will vary wildly from the mathematically-derived volume of a coin when based on a simple 3D model equation taken from a perfect cylinder.
Take the volumetric equation for a cylinder, V = pi (radius squared) * (height). That would be 3.14 times (half the diameter of a Gold Eagle (32.70mm), according to this U.S. Mint pamphlet, is 16.35mm or 1.64 centimeters (rounding to the 2nd decimal), to keep our units consistent with cubic centimeters), times the height (the stated thickness is 2.88mm, or 0.29 cm, rounding the 2nd decimal.
That would be 3.14 (1.64^2) (0.29) = 2.45 cubic centimeters of volume that a solid cylinder of equal stated dimensions that a Gold Eagle should be composed of should occupy if it had no relief, curved surfaces, concavity, or negative space in the reeding.
That gives us the absolute maximum amount of error possible in practice when actually submerging a coin in distilled water for volume calculation, as it is in this "negative space" (the difference between the SG-calculated volume, and the 3D perfect-cylinder calculated model). In other words, if you submerged a 1oz Gold Eagle in distilled water, and got a water displacement figure of lower than 1.91 CC's of space, or higher than 2.45 CC's of space, then you have either performed the test incorrectly (using incorrect water composition can cause variation, as can inaccurate scale, or using an implement that occupies too much space to suspend the coin in the water, can all cause the number to go up or down respectively) - or you have a fake coin which occupies too much or not enough volume of space. Either one is possible in this case. If this happens to you, recalibrate and carefully inspect your equipment, and if you keep getting bad results bring the coin to an expert for verification.
So now that we have our mathematical estimates, and know our anticipated range for upper and lower limits, I shall proceed to conduct the test on my coin. I will update you all once I have conducted it.
Just wanted to quote this for you so it is not lost with another edit.
Is that a yes?
See http://www.doubledimes.com for a free online reference for US twenty-cent pieces
I believe there were some later dated AGE's struck on AGbuffalo planchets. That mwould throw a curve into weight. I vaguely recall one auctioned for some big money. Maybe someone on the board has the skinny on these.
Your 3D cylinder error check relies on Mint stated width and thickness. Did you confirm that .288 cm is the planchet thickness or more likely the coin thickness measured at the rim after striking? I recommend you get a micrometer and check these two numbers to be sure.
Also, mathematically you should never round to 2 places before multiplying. You should use the full Mint and more significant digits on pi information and then round if you choose to. So 3.1416 * 1.635^2*.288 or 2.4187 or 2.42cc which is a better compare than 2.45. However, the fact that you calculated 1.91cc to be the more correct mathematical volume, the 2.42 figure proves to me the Mint thickness is overstated and is the rim thickness after minting, and so this cross check is irrelevant.
If you can actually measure volume to the nearest 1/100 of a cc, just compare your result to the 1.91cc you calculated and see the variance.
But seriously, is this really worth the trouble to get another questionable result? The proof eagle pictured is genuine.
National Commemorative Medals of the U.S. Mint:
https://www.pcgs.com/setregistry/u-s-coins/medals-tokens/national-commemorative-medals-united-states-mint-1940-present/alltimeset/195526
I am sitting here with my 1oz Proof Gold Eagle some distilled water and some string. I am just not smart enough to figure out all this stuff. I think I will send it to PCGS and have them soak it in water for me.
I love it when simple things are made complicated by over-thinking.
FACT: Unless you have the perfect set-up - controlled temp, closed and vibration-free balance accurate to +/- .00001 or more, platinum suspension wire as thin as three hairs, and then clean the object and remove any bubbles MOST OF WHICH you will not be able to see, etc., etc, etc. and then run the test at least three times in your "Clean Room," you won't have a chance of coming up with anything but a very good approximation. The smaller and lighter the coin, the harder it is. Try taking a worthwhile SG of a California fractional 25c. LOL.
That said, if you are very careful and have some of the above, you can weed out some fakes but the usual result is this. You can take the SG of a dozen .999 fine Gold Bullion pieces or a dozen .917 fine Saints and the results will be different than the posted scientific data or that from the mint. Nevertheless, you will be able to tell an object is not gold plated. All this in a shorter time than it took to read the post I just quoted.
PS I rarely run a time-consuming SG test anymore (except on rare occasions) because for several decades any really deceptive C/F virtually always will pass an SG. However, I had to do almost thirty SG's on Russian medals last week because I could tell a few were plated using a scope alone. Because of "the bad company in the group, the SG test caught about a half dozen more altered pieces.
Think you have way too much time on your hands
Redstone,
Hey, PM me and I'll steer you to a forum where your research, expertise, and insight will really be appreciated!
String or thread is a no.no.