Weight tolerance of coins for authenticity

A gentleman can only concede your point here, because for your purposes - assuming the designated example could not possibly have lost any weight whatsoever to any collision or mishap - your definition of "70" is quite sufficient.

Just understand that the fanaticism with which some approach Morgans means that we know how many exist in MS69 slabs, when they last appeared at auction and how much they sold for, if that information were available. There are ten, but it is not certain that one or more may be spurious because of resubmission; not all ten have appeared publicly.

That fanaticism also supports your conclusions about weight loss; it's another statistic a true Morgan fan is expected to have at their fingertips from personal experience. I've weighed hundreds and I'm small-time by any definition.

 

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Thanks for the gracious reply, Superdave. I should have taken the sensibilities of the true afficianado into account from the beginning, and explained up front that none of the coins in my study had ever been professionally graded, and that my "ratings" were actually "groupings" for a special purpose and accordingly adjusted. I'm strictly an amateur when it comes to numismatics. When I was a kid in the 1960's, my grandfather gave me some Morgan silver dollars for Christmas (1964 was, I believe, when the Treasury released a huge volume of them to the public). I loved them (and still think that they are the most beautiful coin the US has ever minted) but, alas, Keep political comments out of threads Edited, the price of silver skyrocketed and I foolishly sold them. (I was in college and needed the cash.) Now in my later years, I've decided to put together a nice collection of 'Americana'... (coins from a day when our money was still actually worth something) for my children to appreciate. Needless to say, my Morgan dollars are the centerpiece of it all. Given the concern these days about counterfeiting, and that I'm a metallurgist with access to an excellent lab scale to calibrate my home scale against, I decided to run a small study, just to approximate the weight loss due to abrasion and erosion from normal circulation. When it comes to bag marks and handling scratches, I strongly suspect that no appreciable metal is lost (unless due to a very severe gouge, which would be uncommon and visually obvious). As for circulation wear, I was happy to find that, for any decent coin of VF or better, one could probably take <=1% weight loss as a good standard for checking a coin's authenticity. Whether or not this would hold true for other types of coins with different materials and designs, I would hesitate to say without running a similar review.

 

How about a hand-held XRF?

 

Read the posts above about specific gravity tests. Decades ago I learned from an authenticator that the ANA authentication service used a Mettler balance good to .001 for specific gravity tests. The balance was on a granite table. Later, while at the first grading and authentication service - INSAB he upgraded to a Sartorious balance good to .0001 for the same test. In his experience, alloys of copper were very difficult to determine. One story he told that should drive an authenticator nuts was to send in a well circulated War nickel and claim it was struck off-metal on a nickel blank!

For example, nickels should be 8.9 and War nickels 9.3. He said the guys could usually not tell if a circulated War nickel was struck on a silver or nickel blank!

These days, the EXPENSIVE hand held units are the way to go as many modern fakes have traces of elements they should not have.