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 Replies: 10 / Views: 1,455 |
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Pillar of the Community
United Kingdom
616 Posts |
Looking at the specs for these 3 coins I am confused how they can weigh the same. Can anyone explain this to me? 2013 10 oz Silver Armenia 5000 Drams Noah's Ark Coin Diameter: 75.5 mm Thickness: 7.4 mm 2013 10 oz Silver Koala Diameter: 75.60 mm Thickness: 8.70 mm 2013 10 oz Silver Australian Kookaburra Diameter: 75.6 mm Thickness: 8.7 mm |
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Pillar of the Community
United States
1391 Posts |
I am not sure if this is the case with the coins you are asking about, but I had a similar question with some Mexican coins. Turns out that (if I remember correctly) the Mexican coins were 1 oz of silver + what ever they alloyed with it. The other coins were 1 oz counting the alloy.
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Pillar of the Community
 United Kingdom
616 Posts |
Well they state on the coin 10 oz. .999 Silver so that should include alloy or wouldn't the purity be different?
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Pillar of the Community
United States
1200 Posts |
Just a guess, but... Not all of the coin is full thickness (i.e: thickness of the blank before the coin was stamped). These kind of differences may be the result of how
much of the coin is stamped down to a thickness less than rim thickness (which I presume is the reading used for the thickness cited in the coin specs) and how
much less than rim thickness it's stamped down to.
Edited by Fat Freddy
04/28/2013 2:52 pm
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Valued Member
Ireland
131 Posts |
As these coins are not purely flat metal discs there will be differences in the 'thickness' of each at a multitude of different points therefore one can't just take the given measurements and come up with a figure for the comparable 'volume' of each.
Norm
edit: Spent a few minutes trying to word that but Fat Freddy put it so much better probably without even trying lol
Edited by Spikey Norman
04/28/2013 2:32 pm
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Valued Member
United Kingdom
90 Posts |
Also, it can be hard to get exact facts regarding coins specs as different websites often contradict each other. Sometimes you see 31.1 written as w Troy ounce, sometimes 31.21, sometimes they get the dimensions wrong too.
Having said all that. I have noticed my 1oz Armenian are a bit lighter than the silver Britannias. Armenian are closer to 31.1 grams, Britannia closer to 31.2, even thought they're both supposed to be .999 silver and exactly 1 Troy ounce. Go figure..
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Pillar of the Community
Canada
1502 Posts |
thickness is not an average of the thickness over the entire surface of the coin, just the rim. Just like how the diameter won't take into account the grooved edges.
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Pillar of the Community
United States
2543 Posts |
Quote:
Mexican coins were 1 oz of silver + what ever they alloyed with it. The other coins were 1 oz counting the alloy. Generally when you are dealing with bullion coins, 1oz, 2, 5, 10oz means the silver content, not the total weight of the coins. An American Silver Eagle is 1 troy ounce of silver, but it is marked .999 fine. In actuality the coin weighs 31.103 ounces 999/1000ths of that is silver the rest is copper .003 of an ounce. So the coin is still 1oz of silver but since the coin weighs in excess of 1oz it is not pure silver. Mexican Libertads/Onzas from 1982 on, are 1oz .999 coins prior to that , in 1949,'78-'80, they were 1oz coin but only.925 silver. |
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Valued Member
United States
456 Posts |
Considering all the coins in question are 0.999 fine, they should all weight the same amount, down to the tenth of a gram or so I would suspect. If you figure 10 troy ounces weights 311 grams, 311/0.999 = 311.3 grams total weight, or and extra 0.3 grams from the last 0.1% to ensure you have 10 full troy ounces of silver. Considering the density of silver is 9.32 g/cm^3, that corresponds to a volume of 33.4 cm^3.
For the Noah's Ark, calculating the volume based on the dimensions provided is: (pi)(radius)^2*(thickness)
(3.1416)(75.5/2)^2*(7.4) = 33,130 mm^3 = 33.13 cm^3, which is smaller than the necessary volume for 10 troy ounces as calculated above. That's not much difference, and I suppose there could be a rounding error somewhere, but I'm betting the coins is probably thicker than advertised considering the rim will be thicker than the fields of the coin.
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Valued Member
United States
456 Posts |
Starbux, now that you have the Noah's Ark 10 oz, how do the dimensions compare to what you stated in the original post?
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Pillar of the Community
United Kingdom
616 Posts |
Trying to measure it within the capsule it appears to be slightly larger in diameter. But I can't be sure. The obverse on the coins is wonderful.
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Replies: 10 / Views: 1,455 |
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Posted 04/28/2013 1:48 pm
