Weight tolerance of coins for authenticity

If you are careful with your weighings, and make sure you don't trap any air bubbles on the coin when you get your wet weight you should be able to tell them apart by SG. I would use a scale accurate to at least two decimal places and only trus your SG results to one place. If your scale is more precise (three places or more you might be able to get the SG to two places. As the precision increases though you have to start making allowances for air currents and shield the scales, and you also have to start having to control the temperature of the air and water.

 

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Thanks. I always wondered about this. It seems a lot harder to do than I thought, (esp. with increasing precision) and makes me wonder if it's necessary to do this in a more controlled environment, and with people who know what they're doing, like in a lab at the university or something.

 

If you want high precision then yes it would probably be better done in a lab, but if you are just trying to get that first decimal place, that can be done at home without too much trouble. And in most cases that first decimal place is good enough. If you are trying to distinguish between two material that are similar enough that you have to go to two places or more you are probably in over your head anyway.

 

I still use it occasionally for gemstones and rough stones. I use a lab surplus mettler H30 with enclosed pan area and it has a usable .0001g resolution. However since some bullion places are buying something like this, one might pay a fee to have a coin zapped for analysis. Here, in So.Cal., one mining specialist on Craigs List advertises an analysis , one time for $50, or 5 for $199.
http://www.olympus-ims.com/xrf-xrd/delta-handheld/delta-alloy/

 

You guys are a wealth of knowledge about this subject.

Thanks for your insights. Wow: .0001g resolution? I bet you have to control for temperature, too.

I will look up people here (Minnesota) that offer that service. I think that may be a better route, esp. if I need higher resolution.

 

I also use a scale with a .0001 gram resolution. I don't control for temperature or even use distilled or deionized water, but I don't consider the SG results I get to be accurate past the second decimal and I consider that place to be +/- .02

 

I have weighed over 100 Morgan silver dollars on a US Balance electronic sscae, their condition ranging from AG-3 to MS-70. The mint standard is 26.73 gm. The published tolerance is .097 gm but this is for the mint's tolerance only, without reference to scale error or coin wear. I found that the most heavily worn coins (AG) weighed on average 25.5 gm... thus showing slightly less than 5% weight loss. However, loss as a function of wear (rating) was NOT linear. From high-side EF to MS showed very little wear. Most wear in weight loss occurred from EF down to Fine / VG. Hence, the "real" standard often cited... +/- 1%, is reasonable for EF-MS coins. For coins showing more wear, up to 4 to 5% might be seen. But, fortunately, counterfeits almost never show that much wear.

 

Very informative posts on coin weights. I personally weigh all silver coins that I buy with a good gram scale.

I consider it the first line of defense when checking if the coin is genuine. Many counterfeits are too light, I've seen some that were 2.5 grams too light on coins that were at least VF

 

Where did you find an MS-70 Morgan? One of those would be news to everyone, including the TPG's.

 

In my experience, any counterfeit that does not weigh within tolerance can be detected by a TPG with their unaided eye about 6 inches away.

 

I know exactly what you are saying...but for the sake of those that are new to numismatics can you give examples:

A Peace Dollar is supposed to weigh 26.73 grams then with the tolerance given it should weigh no more of less than - [ numerical ANSWER HERE ] and so forth and so forth...

A Morgan Dollar...

A Franklin Half Dollar....


Thanks for all your expertise and patience.

 

Or, perhaps, doing some math....

Honestly, I find the "feed me" mentality incredibly irritating, especially in a hobby based upon scholarship.

 

"I find the "feed me" mentality incredibly irritating," True, but keep in mind that this is the internet. Some of the posters could be children or teens, or could be people just now getting involved in coin collecting for the first time. As for math skills, I never cease to be amazed at the lack of basic arithmetic skills among my fellow Americans. I think the public schools have made a major error over the last many years in teaching both math and reading. Kids today have, on average, very poor skills at both. Something has clearly changed.

 

Oh, there are MS-70 Morgans out there. I rated them myself, of course, and I am not a professional appraiser (although I am an experienced collector and a professional metallurgist). My purpose was to see if I could effectively correlate weight loss to rating, so an MS-65 vs 70 proved to be irrelevant to the study.

 

I would very much like to see one, in sharply-focused images of no less than 2000px diameter, which is about the minimum standard for resolution capable of clearly showing the perfection of a 70. Flawless strike, no visible marks. A genuine MS70 Morgan would be a million-dollar coin, and if you've seen "them" (multiples) you should be very wealthy now.

 

BC, There are NO MS-70 Morgan dollars so you'll need to adjust your parameters for that grade.

Now, for what you are trying to do (It has been tried at least two times that I know of a very loooooooooong time ago) just about any Uncirculated dollar will do.

 

Sounds good, looks good, should work...short answer NO, not with any tools available to most of us .

 

On the subject of Morgan ratings, I should be more specific. My reference for ratings was the ANA Grading Standards for United States Coins, 6th ed., along with the 2015 'Red Book' and the 2009 Professional Edition Guidebook. The grading standards permit, and define, MS-70 for Morgan silver dollars. However, the probability that a professional rating service would provide any existing Morgan with an MS-70 rating or not is indeed low. The professional edition guidebook does not indicate any auction records (as of 2009) for coins rated MS-70, but it indicates a number of MS-68's and a couple of 69's. The sale prices for these ranged from $20,000 to $450,000. If budging a rating of MS-68 to MS-70 could run the price up into the millions, I fear the pressure on those doing the rating would be enormous. At that level of coin quality, given a ten-fold increase in value, it really gets down to "picking the barely-visible fecal matter with the extremely keen-eyed chickens". But you are correct that the guidebook does not provide any prices reported at auction for MS-70 Morgans. Doesn't mean that none exist, of course, but I agree that their existence is not reported, though the rating is defined in the manual.
As for my own study, if a Morgan dollar had excellent full-field luster on both the obverse and reverse, and if the only traces of imperfection I saw (under 8x lens) were very slight bag and handling scratches that were not clearly visible to the naked eye, then I (very arbitrarily) deemed it "MS-70" for my purposes. However, I only rated my population (118 coins) as: MS-70, MS-60, AU-50, AU/EF-45, EF-40, EF/VF-35, VF-30, VF/F-20, F-12, VG-8, G-4, and "AG" (="sucks"). So you could argue that I "bastardized" the scale for my purposes, bending the ratings (slightly) to fit my actual population. Ironically, since I frequented upscale coin shops rather than bulk silver dealers, I had almost as much trouble finding truly nasty "AG" Morgans as I did finding near-perfect "MS" coins. Dealers didn't bother to put AG Morgan dollars out under the glass on the assumption that nobody would want them. They always have "scrap buckets" with heavily worn silver dimes, quarters, and halves, but I actually had to ask them to dig around for the junk-level Morgans. My suspicion is that a lot of these get melted for scrap when silver is high, because they contain slightly more Ag per dollar face-value than do the lower denominations. Anyway, that's what I did. If there is a numismatic "Commission of High Inquisitors" who want to charge me with heresy, then I freely confess my guilt. "Mea culpa, mea maxima culpa."