Hello: Currently I'm selling all my coins on Ebay. Some of them are Morgan Dollars that were given to me as a gift. I certainly don't want to sell anything that's counterfeit. Is weighing the coin a reasonable way to determine whether it's counterfeit or not? The 1900-O Morgan I have on my desk right now weighs 26.1 grams.
Weight is an indicator, if the coin is too light then it is a fair bet it's a fake. But there are many fakes made the correct weight and diameter, even with the correct fineness of silver. So correct weight and size do no tell you if the coin is genuine or not. The only way to know is to have somebody who really knows coins tell you if it is genuine or not.
Welcome to CoinTalk. When a Morgan dollar was new, its specified weight was 26.73 grams with a tolerance of about tenth of a gram in either direction. So your 1900-O is a bit light, provided it's not heavily worn, and you haven't said what condition it's in. As GDJMSP points out, though, weight is just one indicator. Do you have any particular reason to suspect that any of your coins might be counterfeit?
I have no reason to suspect that the coins are counterfeit. Though, I've read that there are many counterfeit out there, so I got paranoid. Here is a picture of the coin I currently have up on ebay:
As the 1900-O is not at all a rarity, I'd lean pretty definitively toward a well circulated example such as that as being authentic.
Although this coin looks fine, generally you may want to get an opinion prior to listing a coin for sale rather than after.
