Silver Loss from Wear on 90% Silver Coins (calculation)

This is the key assertion, and one that I think we'll be able to test.

I'm becoming more convinced that the primary "wear process" is not "squashing down", but actual removal of metal. How do we determine which of us is right?

I agree with your assertion that coins in XF or AU will usually be within weight tolerance. I don't think it's because metal has been "pushed around" instead of "worn off", though -- I believe it's because metal has been "worn off", but it's not enough to take most coins out of tolerance. (Remember, those two Roosies I posted are actually slightly above specified weight, although still within tolerance -- they could afford to lose more than a coin with "low birth weight".)

I could take a few BU pennies, rub them on cloth for a while, and see whether there's a demonstrable loss of weight. I don't know, though, whether that would count as "typical wear". So, what would constitute a reasonable simulation of typical wear? Carrying them in my pocket with my keys? Running them through the laundry a few times? (I've got some very shiny, but very beaten-up quarters that my son forgot to take out of his pocket before laundry day!) I want to do some sort of longitudinal test, following the same coin as it wears, because it's hard to compare coins that may have started out at different weights. If I can't do that, I need to get statistics from lots (hundreds) of coins; that would be tedious at best, and I don't trust my grading skills enough to group coins accurately into grade bins.

I've got my own ideas as to what goes on as a coin wears, but I'm not nearly so interested in "defending" those ideas as in finding out what's happening. Now I've got some equipment that will let me get the measurements I need. Let's come up with some testing procedures!

 

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Well I disagree with Doug a touch here. I would say the law of large numbers should show that there are as many overweights as underweights, and as such just because a bag of F coins are within tolerances of the low end, the average should not show weight loss. If a bag of newly minted dimes weigh 100 pounds for example, saying the same count of dimes in F condition weighing 99.7 pounds is within tolerance is not really true. Technically its true, but it should have been 100 pounds if there were no weight loss. You cannot assume ALL of the dimes were ALL underweight coming from the mint, so therefor no weight loss has occurred. Tolerances are fine for individual coins, but shouldn't be in summary if the mint was truly putting in the silver they have said they did in our coinage.

Sorry, but my stat classes are just coming back up, and statistically I do not think that argument is valid. The only way to prove it, though, would be to have large bags of dimes, all of certain wear degrees, and weigh them. Even then you would have sampling error, so multiple bags in each grade would be required to PROVE it within a statistically meaningful way.

I do not wish to go through this exercise, but if someone does it would be great. From my own experience I know to discount weight on heavily worn coins, (ie do not assume it is counterfeit if under tolerances). If any coin F up is not within tolerances I would immediately suspect a counterfeit.

 

I'd like to see a full bag of Kennedy's, a full bag of Franklin's, and a full bag of Walkers all weighed at the same time. We're assuming identical bags. Anyone want to guess which bag will weigh the most.

 

Doesn't that depend on the levels of wear? I would guess that a bag of uncirculated Franklin's would likely weigh more than a bag of circulated Kennedy's.

 

No APPRECIABLE weight loss due to wear.

 

I have noticed that a stack of 20 Barber halves is the same height as a stack of 15 Walkers/Frankies/JFK.
Is this due to loss of metal due to wear or were Barbers just thinner?

Just went back and weighed them. Barbers are running 11.5g and all others are running 12.5g.

 

As I might have suspected, we aren't the first to consider the nature and significance of metal loss due to coin wear.

Money and the Mechanism of Exchange, by William Stanley Jevons, 1875, Chapter XIII: Technical Matters Relating to Coinage

I haven't read enough of the rest of the book to know how long this "old silver money" had been circulated before it was withdrawn. One wonders what its numismatic condition would have been. The German word "glatt" comes to mind...

 

with silver at $1.1 per ram, i don't think it matters so much

 

i think dealers should weigh out the junk silver when you buy some, and take the eight and multiply it by .9 because thier 90% silver

 

Two years, and I still haven't gotten around to the work I promised earlier in this thread.

 

And do you think the dealer should do the same when they buy? Or would you feel as if this was then just a tactic to pay less and instead take your silver to someone who buys by X face?

 

I'm sure he'd like to buy by either FV or weight, whichever is LOWER, and sell by either FV or weight, whichever is HIGHER. At least, that's what I try to do.

 

Interesting article. This will help to identify some counterfit coins coming out of china. They are making copies of pesos & canada dollars in VF or better condition for sale on ebay - they look pretty good detail wise,but they are about 20% under weight.

 

Welcome to CoinTalk! If you've got the time, it might be interesting for you to create a new thread or two describing your purchases and what you've found. Posting to very old threads (this one was last active in 2012) can cause some confusion, as people start reading the thread from the beginning and responding to other older comments.

We frequently discuss Chinese fakes here, and getting more information about them is always helpful.

Again, welcome!

 

I can speak to some of the issues raised, particularly by GDJMSP, from the perspective of corroded early coppers. I've done a number of tests on early copper cents that were corroded and from which the corrosion had been removed. Basically, even the removal of heavy corrosion has very little effect on the mass of the coin. This was quite surprising to me, but It was consistent.

It's intuitive to think that much of the mass of the coin should be gone when it reaches Good, but when you think about the fact that the great majority of the mass of the coin is in the non-raised parts of the coin, the fact that very little metal wears away during circulation should not be surprising.