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How much metal is lost by weight from wear during circulation?

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This info must be available somewhere, someone must have done gradings and weighings, what were the results, and the source of the information? You'd think that buyers of 90% silver coins by face value should know how much they're losing when they get heavily worn pieces.

 

Starting with freshly minted coins from any series, on average how much metal is lost, by weight, during circulation as we go down the scale from mint state to AU to XF to VF to F to VG etc.?

 

It will probably vary slightly with different metals and alloys, with the sizes and thicknesses of the coins, and even with different design elements and rim styles.

 

I'd be interested in knowing the results from for example buffalo nickels, mercury dimes, lettered-edge capped bust halves, and wheat Lincoln cents.

 

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Experiments by the mint in the early 20th century showed that silver coins being returned to the mint lost about 5% of their weight.

 

A limited experiment run by myself showed about a 3%-4% loss on wheat pennies from UNC to G. I haven't done nearly as exhaustive research as you request, but these results seem like they would be fairly typical.

 

As an application, never buy 90% silver by face - always buy by weight.

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Somebody once came into the coin shop with a bunch of really well-worn junk silver that would commonly be called "slicks." Think Barber and Merc dimes and SL quarters where you could barely see the type.We bought it by weight and sent it to the refinery along with other stuff we culled from our junk silver. We would not sell such coins as common junk silver. but perhaps other people do.

 

Out of curiosity I weighed parts of it as 10-coin lots, and on average they were 7% light. Later on a different deal of slick Morgan dollars I weighed them and again they were about 7% light.

 

Common junk silver probably runs about 2-3% light. It is what it is.

 

Hope this helps.

 

TD

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Thanks PhysicsFan & CaptH for those helpful responses, the weight losses you both documented are less than I'd have expected, I'd been thinking 10% or even more reduction in weight after the recognizable surface features of a coin are considerably eroded.

 

This won't affect the weight per se, but I can imagine there's an accelerating effect of erosion, meaning that the more eroded a coin is, the faster it will then be worn down in the future, for without the protection of the higher detail of the devices, more surface is exposed to regular rubbing and ordinary contact. And in that regard, the more eroded a coin, the more it will continue to be handled and exchanged, as by Gresham's Law, it has become an inferior measure of value.

 

 

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Just remembered - I still have a pdf copy of the mints report on the subject that someone sent me (probably Roger, I think). It was part of the 1902 mint report. If you want a copy, PM me your email address.

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There is a discussion of abrasion of silver coins in the Mint Annual Report for the Fiscal Year ending June 30, 1902.

 

Unfortunately, the report itself doesn't seem to be available in digital form.

 

However, the Mint Director's annual report is also included in the Annual Report of the Secretary of the Treasury. The report for 1902 is available in digital form here.

 

For some reason, the link doesn't take you to the right page, so click the link and then scroll down to page 291. (You can click on the "page" button on the top right of the page [which says "Front Cover"], which will allow you to jump to the chapter nearest the page you want.)

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I've seen heavily worn Barber dimes and Standing quarters that had lost 12% of their weight. In extreme examples weight loss can hit 15%.

 

Wow, that's hard to believe...that's 1/8th of the coin disappearing....if 15%, almost 1/6th !!

 

It just doesn't seem that the smoothing over decades can eliminate that much mass, but I guess they tested for it. Still seems excessive.

 

Maybe most of the valuable metal is on the outside with these coins and the less-valuable stuff that is not getting worn down is protected ?? Sort of like the candy center of a Tootsie-Roll Pop ???:grin:

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I don't have a 1902 Mint Report. The 1903, on P. 17, has a table showing the results of recoinage of uncurrent subsidiary silver coins from FY1891 to FY1903.

 

Out of a total of $65,147,833.87 face value in worn out coins recoi9ned, they produced $62,146,743.47 in new coin (I am assuming that that

precise but odd face value represents the face value of the recovered silver if it were to all be coined, there obviously being some odd scrap left over.)

 

The loss by weight was equivalent to $3,001,090.40. Divide that by $65,147,833.87 and you get the percentage of weight lost, about 4.6%.

 

This would not necessarily include only well-worn coins, as it could also include coins that were near full weight but damaged.

 

TD

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I've seen heavily worn Barber dimes and Standing quarters that had lost 12% of their weight. In extreme examples weight loss can hit 15%.

 

Wow, that's hard to believe...that's 1/8th of the coin disappearing....if 15%, almost 1/6th !!

 

It just doesn't seem that the smoothing over decades can eliminate that much mass, but I guess they tested for it. Still seems excessive.

 

Maybe most of the valuable metal is on the outside with these coins and the less-valuable stuff that is not getting worn down is protected ?? Sort of like the candy center of a Tootsie-Roll Pop ???:grin:

 

I use to BST 90% junk silver all the time and believe me, some 100 year old dimes and quarters that circulated for 50 years are nothing but thin blank disks. They appear to be less than half of the nominal minted thickness, so it's almost surprising they retain 85%+ of the original weight.

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This would not necessarily include only well-worn coins, as it could also include coins that were near full weight but damaged. TD

 

That's an excellent point, the mint's figures for weight reduction of coins melted for reminting did not only reflect abrasion, but included others with perhaps little wear but mutilated in one way or another, such as by being bent or counterstamped or holed.

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Many thanks to PhysicsFan for emailing me the Mint report for 1902 with details about silver coin weight loss to abrasion and other factors, in which the coins being melted were separated by year date, and then also by whether it was done at the P mint or the NO mint. I understand the report was originally obtained from RWB who thus deserves acknowledgement.

 

Here's a compelling snippet: at the New Orleans mint, silver coins being remelted that no longer had readable dates had the following weight losses:

halves - 27% loss

quarters - 29% loss

dimes - 32% loss

 

 

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Many thanks to PhysicsFan for emailing me the Mint report for 1902 with details about silver coin weight loss to abrasion and other factors, in which the coins being melted were separated by year date, and then also by whether it was done at the P mint or the NO mint. I understand the report was originally obtained from RWB who thus deserves acknowledgement.

 

Here's a compelling snippet: at the New Orleans mint, silver coins being remelted that no longer had readable dates had the following weight losses:

halves - 27% loss

quarters - 29% loss

dimes - 32% loss

 

 

I wonder, at those percentages, how many were holed coins.

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When you think about it....unless they were in bags with similar-strength coins...even over long periods of time....what would cause that much abrasion beyond vulnerable high-relief points ?

 

Think about it....the average quarter....spends time in your pocket (soft)...pocketbook (soft)....with other quarters until you spend it (days/weeks/months of no movement).....given to a merchant, it sits in the cash register under or on top of other coins....or in a vending machine (also no movement).....at first touch, these are hard metal coins with hardening agents added....think of how long it takes running water to erode rocks, much more vulnerable.

 

Too bad we can't put a micro-GPS on a coin and detail its life history ! :grin:

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Earlier tests were done on gold coins -- mostly gold dollars.

 

The Royal Mint made extensive tests of coin hardness in the 1880s. The sources are in the bibliography of From Mine to Mint.

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Earlier tests were done on gold coins -- mostly gold dollars. The Royal Mint made extensive tests of coin hardness in the 1880s. The sources are in the bibliography of From Mine to Mint.

 

I've only recently ordered From Mine to Mint, but my designated copy is awaiting the application of an autograph by the author, hint hint, ahem.

 

With gold, might it have been profitable in earlier years to erode batches of the coins inside a rock tumbler, and harvest the gold dust?

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Shaking a bag of gold coins was easy to do and was common practice among Swiss bankers who then sold small quantities as if the coins were full weight. However, the US mint had very tight tolerances for bags of new gold, so this did not work well domestically. Exported gold was valued entirely by weight.

 

I am autographing a bunch of copies on Tuesday.

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You'd think that buyers of 90% silver coins by face value should know how much they're losing when they get heavily worn pieces.

As a matter of fact, we do know. "Slick" pieces only weigh between 85% and 90% of their original weight. So when folks bring in a large amount of extremely worn material, we can't honor our "NN times face", and instead have to make an allowance for excessive attrition due to wear.

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