I just bought a small electronic scale (200g max - .01g accuracy) and a 50g calibration weight. Having no experience with weighing coins, I assumed I would find more consistency with mint weights on new uncirculated and proof coins. I don't know if there is a problem with the scale, with the calibration weight, or if there is more variation that I thought with the coins. Here's some results: 2009 Silver Eagles UNC (mint weight=31.101g) - actual weight=31.32 to 31.36 depending on coin 2006 Silver Eagle UNC - actual weight = 31.35 g 2009 Mexican Libertad UNC (mint = 31.100g) - actual weight = 31.05 g 2009 Canadian Maple Leaf Proof (mint = 31.100 g) - actual weight = 31.35 g On the Silver Eagles, the .25g overweight is small (less than 1%) but I suppose I was expecting something that was a bit closer -- and more consistency between coins that are supposed to weigh essentially the same. Any comments?
honestly that doesn't look off, did you try weighing pocket change to check weights, and are you using the tare before weighing each coin?
The American Silver Eagle for sure has a prescribed minimum weight of 31.103 grams, but no variance (+/-) is allowed on the minimum side, but nothing is mentioned as far as a maximum. I suspect the Canadian is similar. So it looks like by allowing a .25+ gram allowance on the high side, it could eliminate weighing each ASE. The 90% US Silver Dollar was 26.73 grams with variance of +.097g to -.097, or a variance of .194 g possible( except for the 1964-D Peace tolerances was +0.39 to -0.39 grams or a .78gram variance ~ Breen). I suspect the Mexico coin was not a guaranteed weight coin, or it was within its variance ( which I don't have at hand). On balances, If you have any air movement when weighing on an open pan, just breathing over it can make a difference. Put a tupperwear container or something over it, especially if calibrating. Jim
Yeah, there is definitely an art to weighing coins. In my case, I was not only taring before each weighing and making sure I was on a level surface (and making sure the A/C was off and not blowing on the scale), but I also calibrated before each weighing. And I weighed each coin multiple times, which would sometimes result in a .01g difference. It seems that in the case of the American and Canadian coins, the 31.101 and 31.100 weights are a guaranteed MINIMUM, not an exact weight. Weighing pocket change is not helpful. For example, a new UNC nickel should be 5g, but my circulated pocket nickels weighed noticeably less, which is understandable.
You also have to realize that the majority of scales you would buy are not the precision instrunments you might think they are. They are all going to be off a little. But a good rule of thumb is that if the coin is within 1% of legal weight then that coin is OK weight wise. Just remember that more, or less, than that is cause for some concern. And - the correct weight, while an indicator of authenticity, is not proof of authenticity. And coins, even well worn coins, should still be very close to the correct weight. Coins actually lose very little weight due to wear.
