I found that 1 troy oz = 31.1034768 grams but I'm not sure how weight factors in for other purities. I'm wondering if anyone knows what .720 silver should be weighted, and maybe more importantly how you go about accounting for the weight of the different metals. Or is it just always a troy oz and I'm overthinking things, and you just use the metal ratios to calculate the value alone? I weighed a .999 libertad against a 1968 .720 Mexican Olympic coin using the beam scale from the kitchen and the libertad is noticably heavier so it seems like purity does affect weight, but the Olympic coin is one I am concerned about maybe being faked so I don't know if that's a good litmus test either.
Take the weight of mexico olympic coin and multiply by fineness (.720) to get the actual silver weight.
Well what I'm trying to do is calculate what the weight should be so I can confirm that it weighs accordingly. I don't have any other .720 coins to compare to unfortunately. It would be nice to identify the proper formula.
According to Krause, it should weigh 22.5 grams. The Krause catalog lists all the various weights of world coins, it is a good investment, even for an older used one.
Depends which one is the troy pound Thanks for the info Chip. I can probably deduce the rest from there.
I found a site showing this coin as having 0.5209 troy ounces of silver. 0.5209 troy ounces * 31.1034 grams / 1 troy oz = 16.2 grams silver out of 22.5 grams 16.2 / 22.5 = .720 It appears you can't really use a formula based on the purity unless the weight is also on the coin since, as in this case, it is 72% of an unlabelled weight. In cases where the weight is listed then you can just do a direct oz to gram conversion without worrying about the content. However, if you know how many ounces of silver are supposed to be in the coin you can use that to calculate the total weight based on purity. 0.5209 * 31.1034768 / 0.720 = 22.5025 total grams
