Verifying coins

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#1 Thu, Apr 19, 2012 - 2:26pm
pourty
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Verifying coins

My tinfoil is tight, so I like to make sure what I ordered is actually what I got.

The published specifications for American Gold Eagles are as follows:

Weight: 33.933 g

Diameter: 32.7 mm

Thickness: 2.87 mm

So today I measured 4 of these, and this is the range I have found:

Weight: 33.94 g - 33.96 g

Diameter: 32.69 mm - 32.73 mm (the diameter will vary around a single coin by as much as this)

Thickness: 2.794 - 2.845 mm (measuring the edge of the coin, again, it may vary by this much depending where on the coin the thickness is measured).

Anyone else take similar measurements? I'd be interested in results to compare with what I've found. I think the measurements I've got are very reasonable for these coins.

Edited by: pourty on Nov 8, 2014 - 5:30am
Sun, Apr 22, 2012 - 8:42pm
wje3
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Verifying Coins

Pourty;

Can you tell me about the instruments you used to take your measurements? I assume it's a digital scale and a calipers and I'm looking into purchasing a set. What brand are they?

Thanks.

Tue, Apr 24, 2012 - 5:42pm (Reply to #2)
pourty
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wje3

I reload ammunition for my firearms, so I have tools at hand. 

The scale I'm using is an RCBS 1500. It's a rather pricey scale made for reloading, you can probably find something much cheaper that will do the job just fine for measuring coins. A lot of people use pocket scales (like the Frankford Arsenal scale for under $40: https://www.midwayusa.com/product/175512/frankford-arsenal-ds-750-electr...) Funny, I've got this pocket scale, and I think I only paid $20 a few years ago. It should work fine for this sort of thing. These scales will measure down to 1/100th of a gram.

I'm also using reloading calipers by RCBS (I recommend dial calipers so you're not at the mercy of batteries): https://www.midwayusa.com/product/630852/rcbs-dial-caliper-6-stainless-s.... The calipers will measure down to 1/1000th of an inch. 

As coins specs are in millimeters, you'll need to either get metric calipers or do the conversion, the conversion is simple: 1 inch = 25.4 mm.

I've measured several Krug's and Eagles now. They are the same specs. I see a range of + / - 0.03 grams in weight, and a range of up +0.012 / - 0.003 of an inch for diameter, and a range of +0.006 / - 0.000 of an inch for thickness. (yes, 0.000, that's not a typo, I didn't find any less than the stated thickness)

The only coin which was under stated weight was a 1975 Krug, incidently, it was the coin that was the exact stated thickness as well, so I guess that makes sense?

I'm really interested to know what the acceptable tolerances are for these coins (and maples as well).

Tue, Apr 24, 2012 - 5:42pm
pourty
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About thickness and diameter...

Also note that the thickness and diameter of the coins is not constant, as with anything, there is a tolerance. I have found that the Eagles/Krug's can have a range of around + / - 0.003 inches measuring different spots around the same coin. I measure them in several spots and use the most common number I see for my calculations.

Tue, Apr 24, 2012 - 5:49pm
pourty
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Diameter & Weight

This site (https://www.inexpensivegold.com/gold-blog/how-to-detect-counterfeit-gold...) mentions that a weight delta of greater than 1% is suspect (all mine were within the 1% envelope). It also states that a diameter less than stated is something to look for when verifying coins, thankfully, all mine were at or slightly over the specified diameter.

Sites I've read state that thickness is not as well controlled, which probably accounts for the larger variations I'm seeing in thickness (I'm measuring around the coin edge).

Tue, Apr 24, 2012 - 7:26pm (Reply to #5)
wje3
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Thanks for all the

Thanks for all the information, Pourty.

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