I had a coin collecting friend show me a 1868 Seated Liberty Half the other day and as soon as I saw it I told him it was a fake. I was picking at him but the comment started something. We decided that one of the best ways to indicate a fake was to weigh it and so we did. The weight of the coin was over 12.4 grams by about .8 grams. Well at that point I learned that I for one could not find any information on tolerance by weight. Everyone there just assumed that what little dirt was on the coin was making up the difference. What do you guys and gals think about this and more importantly where do you find the tolerances for weight in coins? The coin was probably a XF and in really nice shape "no damage". He was asking $100.00 for it, but I can't afford a $100.00 lesson in detecting a fake coin.
If it was me I would weight it on a .001 gram scale, as .8 gram on a .01 scale could mean that it was over by as much as .87 or as little as .78. If it is .8 gram over I would suspect it as a fake unless it is very dirty, but you say it is probably an XF which means it shouldn't be that dirty. An XF 1868 is listed over $200 in the book and for the price he is asking I would stay away from it. This is just my opinion but I ran into a trade dollar a while back and it was overweight by .057 gram in VF condition and it turned out to be a fake, and I learned very expensively by that. Marion
I think weight is only one factor, at least with bullion gold coins. You also have to consider the diameter and the thickness.
The coin is between 6 and 7% overweight, which is well beyond the mint's tolerances. It is a fake! You did well to avoid it.
For most 19th Century and later coins, Krause will mention it if there are substantial weight variations in the genuine article. Absent such a notation, underweight or overweight by more than 1% or so confirms that the item is a fake. But always remember, when you see a 22g weight given for a 19th Century silver crown, that should be in the 26-28g range, you can run, not walk, to the nearest exit; but just because the weight is right absolutely does not confirm that a coin is genuine. If I were going to make a fake 1876 Japanese gold 2 yen piece you can bet your life I would use 3.3333g of .900 gold! Investing ~$70 in raw materials for creating a $75,000 "coin" would certainly not be a problem.
The coin is way overweight. An 1868 half dollar should weigh 12.44 grams with a tolerance of +/- .097 grams. So it is overweight by almost 7 times the legal limit. Best place to get a listing of the tolerances would be to get ahold of a copy of the Coin World Almanac. When they show up on eBay they can usually be purchased for about $5 or so. (Personally I would stay away from the Millennium edition (2000). They earlier editions are much better and have more information in them. I have multiple copies of all the editions and refer to them constantly. There is a TREMENDOUS amount of information in them. If you are a subscriber to Coin World or other Amos Press publications you can join Amos Advantage, and if you do a search of their offerings you will find that you can buy a brand new HARDBOUND copy of the 1994 edition for $5. (The softbounds eventually break at the spine and start falling apart. That's why I have multiple copies.)
