Featured Counterfeit Gold Eagles w/pics of core taken out.

Conder, I believe you are the same guy who posted the history of slabs over at CU, right ? Great work and thanks !

With the digital scales today very accurate to 0.01 grams, even if we say they are off by a few multiples of that, I think the weight-check can work for sloppily-made counterfeits and frauds. I agree, if someone has gone the extra length to match up the combined weight of the slab+coin, then this won't help any of us.

 

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Still
There is no hurt in weighing the slab coin

 

None, an easy double-check against a sloppy counterfeiter.

But we do need the different weights for an empty slab for both PCGS and NGC...and then for different years....and then depending on if was used for Double Eagles, MSDs, etc.

 

Weighted a bunch of coins, my measurement first and actual second:

Chinese 1 Oz. Panda: 31.14 vs. 31.10

Canadian Maple Leaf 1 Oz: 31.16 vs. 31.10

American Eagle 1 Oz.: 33.95 vs. 33.93

Austrian Philharmonic: 31.12 vs. 31.10

JFK 1964 1/2 Dollar: 12.52 vs. 12.50

So far...I'd say pretty accurate readings. I may not have even calibrated accurately so I might shave a bit off the wider figures.

But even in the worst case, it was only off by 0.2%. Very impressive, IMO.

 

If Ikes vary by that much, it's almost 5%. Where did you get that figure ? Is that normal for most coins ? I would think it would be less but I'm not an expert on Mint standards, that's for sure.

The greater the coin variance plus any variance in the slab weight (if any) is going to render only the sloppiest of counterfeiters easy to spot, I agree.

But the coins I weighed (above) were off by at most 0.2% whereas yours was off by 4% (20x as much).

 

4%

Weight tolerance figures for the Ike dollars are from the Coin World Almanac 1990 edition Pg 341

Different coin series have different tolerance allowances. Pre 1933 gold tends to be the most strict (.09 to .1%) , followed by pre-1935 silver (.4%). Clad and copper nickel coins tend to be the most lax (usually around 4%). The greatest tolerance allowance is for the 1865 - 1873 nickel 3 cent piece 1.94 grams +/- .259 grams. That is an allowed variance of 13.4% off of the standard.

 

About.com claims, without citation, a tolerance of +/- 0.259g for the 1964 Kennedy. (Oddly, they say current silver proof halves have a tolerance of +/- 0.400g.) As @Conder101 indicated, tolerances for clad coins are apparently +/- 4%.

I'm thinking about tolerance issues as well, so I weighed each coin in a new roll of 1964 Kennedy halves I just received. These are all BU or sliders.

I actually went through the whole roll four times, top to bottom, then bottom to top, then back and forth again. So I went down the first column, up the second, down the third, then up the fourth. This was to make sure there wasn't any kind of "stickiness" between one weighing and the next.

Coin	First	Second	Third	Fourth
1	12.49	12.48	12.48	12.48
2	12.47	12.47	12.46	12.46
3	12.58	12.58	12.58	12.57
4	12.53	12.53	12.53	12.53
5	12.37	12.38	12.37	12.37
6	12.35	12.34	12.34	12.34
7	12.63	12.62	12.63	12.63
8	12.52	12.52	12.53	12.51
9	12.35	12.35	12.34	12.33
10	12.62	12.63	12.62	12.61
11	12.64	12.65	12.65	12.64
12	12.42	12.42	12.42	12.41
13	12.74	12.74	12.74	12.73
14	12.32	12.32	12.31	12.31
15	12.61	12.6	12.59	12.59
16	12.32	12.32	12.31	12.31
17	12.31	12.31	12.31	12.3
18	12.61	12.61	12.61	12.61
19	12.47	12.47	12.47	12.47
20	12.41	12.41	12.41	12.41
Avg	12.488	12.4875	12.485	12.4805

There's a slight downward drift over the course of the experiment, sharper in the last column. The whole process took about 20 minutes, and I'm still using the batteries that shipped with the scale, so low voltage may have been affecting measurements. But it still looks like I'm seeing a pretty solid +/- 1 digit repeatability.

The overall average weight is a bit under the standard 12.5g, but while statistics has never been my strongest subject, I'm pretty sure 12.48525 (for all four columns) or 12.48683 (throwing out the last column) is well within the expected range for a sample size of 20. Even if the actual average weight of the roll is exactly 12.5g, the scale is only off by 1.5 digits at most, which is (IMHO) spectacular for a not-recently calibrated cheap consumer scale. (Of course, the actual weights could be higher, and my scale could be off by more than I think.)

I'd been meaning to do a test like this for a long time. Now I know why I was putting it off. Man, that was tedious. But now I know a lot more about my scale.

 

JeffB, do you calibrate each time you turn it on ?

 

I have never calibrated this scale. Not even once.

 

My ET Matrix comes with a 100 gram weight for calibration. Seems to eliminate about .01-.03 gram error measurement. Even without calibration, it's off by less than 1/10th of a gram.

 

this is why any high valued or gold coin I purchase, I slab. TPGs will do the testing for me. PCGS ftw.

 

Probably...but they are processing stuff so fast that they miss easy counterfeits (for them). When you look at 300-500 coins a day....do the math.....that means probably 45 seconds to 90 seconds tops if you are working 8-10 hour days.

I would feel better if they ran all the coins through a metal spectrograph or whatever and also took UHD pics of the coins to identify the smallest detail and prevent counterfeiting (maybe PCGS is doing that now with their latest programs and slabs).

 

Anybody got some gold and fractional coins in recent NGC holders they can weigh ?

I have a 2013 Buffalo 1 oz. in the Black Slab and a 2010 Libertad 1/2 ounce. Slabs look identical except for the color and size of the hole in the middle If we can get some more 1 oz. coins weighed in NGC slabs as well as the fractionals, it'll help us get a pretty good reading on the weight of an empty slab for a 1 oz., 1/2 oz., 1/4 oz., and 1/10th oz. gold coin.

I know different national coins have different dimensions even for the same weight but the dimensions likely match-up for the same fractional. Meaning, the missing 'doughnut' in the middle should be the same mass-wise.

 

TPG? Testing?

 

absolutely. to determine if its counterfeit. Youre much more likely able to sell a slab bullion coin than an unslabbed one.

 

What makes you think they do any testing?

 

They do look for counterfeits, but I am not sure if they are yet employing any metallurgical testing devices like the equivalent of an X-ray scanner at an airport.

 

If they're guaranteeing that a coin is genuine, they must do some metallurgical testing.

 

Today in Coin World, some dealer in Columbus, Ohio purchased a 1 ounce slabbed gold coin that was fake. Besides the diagnostics not being right, he weighed the slab with the coin and it was 10 grams less than a genuine one. So it does pay to weigh the slabs. At least gives you some kind of start.

 

Thanks, here's the link:

http://www.coinworld.com/news/preci...old-bullion-coins-in-counterfeit-holders.html

Very scary, and why knowing the weights for various slabs with various coins of a certain weight is important. For some coins, the thickness changes which means it is wider and more plastic is taken out (overall weight reduced); for another coin (i.e., 2009 UHR Saint) the overall weight might be higher as the coin is smaller but thicker.