JadeDragon wrote:tinhorn wrote:JadeDragon wrote:If I remember correctly each US copper penny contain 1/10 TROY Ounce of Copper... I own some overstamped pennies that say that.
I hope you're not remembering correctly for two reasons: 1) copper is measured in avoirdupois, not troy, and 2) a 3.1-gram coin is just UNDER 1/10 ozt., but just OVER 1/10 oz. av.
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That is close enough to 1/10 of a troy ounce to be a 1/10th of a troy ounce for me. The difference is in the rounding of the calculation. You can measure anything against any standard or non-standard weight you want. It looks to me that the US government chose to set the weight of a 95% copper penny in troy ounces. This makes some sense since the penny started back when there were silver and gold coins.
JD was perfectly on target here. Nominal design weight of a copper penny per US Mint isn't 3.1. It is
3.11, which to 4 digits is
exactly 1/10 troy ounce.
1 Troy Ounce = 31.10(34768) grams
They can measure it in any system they want to. Commodity copper is traded in avoirdupois, but the mint can (and apparently did) design the copper penny to weigh whatever they wanted in whatever system they wanted, and they clearly and purposefully chose it to weigh 1/10 troy ounce. That means a roll of pennies weighs 5 Troy Oz, and a box 250 Troy Oz. And interestingly enough, that also causes a nominal box of copper pennies to weigh exactly 7775 grams, a semi-round metric number, even though the piece weight is in troy oz.
Note that they chose for the new penny to weigh exactly 2.50 grams, in keeping with the nickel, dime, quarter, and half (except 40% Ag) being in the metric system of 5, 6.25, and 12.5 grams. Nominal net content box weights in grams for 1, 5, 10, 25, and 50 are 6250 (zinc), 10000, 6250, 12500, and 12500 (non 40%) grams.