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Author Topic: Cataloging Estimated Dimensions of Slabbed Coins  (Read 381 times)

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Offline Ken W2

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Cataloging Estimated Dimensions of Slabbed Coins
« on: June 21, 2022, 10:56:45 pm »

Some NGC slabbed coins provide a weight, but many provide no weight or diameter. Diameter can be fairly accurately measured with a good caliper through the slab. Weight presents a harder problem. It occurs to me though that the holders may be fairly uniform in weight, and thus the weight of the coin can be estimated.  Sure there will be some variation, in part because the white insert actually holding the coin will vary based on the diameter of the coin. As a quick test, I weighed 3 NGC slabbed coins and after subtracting the stated weight of the coin the slabs all weighed within .07 grams of each other, and all 3 were nominally 40 grams. If, with a larger sample size, we could determine an NGC slab weighs X grams on average (or NGC provided the speced weight) we could derive an estimated weight to include in attributions and cataloging. So long it was stated to be an estimate, such estimate would not be deceptive and would have the value of confirming the coin is in the appropriate weight range for the issue. 
I’d welcome your opinions about the value of so estimating weights and any info you have about the standard weight of NGC slabs.

Offline Jay GT4

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #1 on: June 21, 2022, 11:12:55 pm »
I don't remember but isn't the weight on the NGC lookup online?

Offline Ken W2

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #2 on: June 22, 2022, 12:39:49 am »

Unless I don’t know where to look, NGC look up only shows the slab and thus you only get the weight if weighing was included in the service selected.  I did a search online and found a thread in which others asserted the empty NGC slab weighs just under 40 grams.  That’s easy enough to confirm by weighing slabbed coins on which the weights are stated and doing the math.  But there will be some variation.  I guess what I’m really asking is whether there is any value in the attribution/cataloging process of so estimating. The only benefits I can see are confirming to coin is not out of the right weight range and having consistency in the items of info included in your attributions. 

Offline Virgil H

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #3 on: June 22, 2022, 01:51:40 am »
I only have two coins that were slabbed and I removed them from the cases as soon as I got them. I never thought to weigh the slabs. And the coins I had were not weighed by NCG that I know of, I weighed them myself.

Anyway, there are a couple ways to look at this. One is the weights of the cases plus the various sized holders and how accurate you can be with those. If those are known, one could get a reasonable weight for the coin. Your numbers that you have come up with so far seem reasonable and would benefit from a larger sample size.

Here is where I am going with this. The biggest question is what level of tolerance are you going for? How accurate do you need to be and at what point would being off make a difference. Many ancient coins have what I consider a large variance in weight. More than I expected when I first started collecting. So, I think that for many coins, a method of weighing the entire slab and subtracting what the estimated slab weight minus coin would be acceptable to many (most?) people.

It really depends on how accurate you want or need to be. I wouldn't do this if I were selling a coin and describing a specific weight, mainly because I am strict about tolerances for things like this. I would want to weigh the coin by itself. That said, no one calibrates scales any longer and, as an old Army calibrator who calibrated scales in commissaries, orderly rooms where people were weighed for the fat boy program, hospitals, and nuclear/conventional weapons storage sites (where weighing projectiles is done regularly to determine deterioration of the weapon), I haven't trusted a scale in years. With a coin, maybe I would say approximate weight or something, plus I may be the only person in the world who cares. Yeah, I know they say digital scales are infallible. I don't believe that. No one calibrates voltmeters anymore, either.

And although it is not really true, the inaccuracy in things weighed in grams is going to appear much more than with something weighed in kilos.

I sure don't trust my cheap China made digital scales any more than the one that weighs the meat I buy (other than I am cynical enough to believe the grocery scale is always going to be wrong in the store's favor). But, that is what we have today. If you can get a good range of weights for slabs with various sized inserts, it is probably OK, although it introduces an additional element of error. And there will always be at least some error.

Virgil

Offline Ken W2

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #4 on: June 22, 2022, 09:31:31 am »

I have 21 NGC slabbed RSCs, but only six have the weight reported by NGC.  When the reported weights are subtracted from the total weight of the slab, the six average 40.09 grams.  BUT, when I tried to use that average weight as a predictor of coin weight, by subtracting 40.09 from the actual total weight of each slab, the estimated weights were off from the actual/reported weight of the coin by a range of .12 to a whopping .47 grams. While that range is close enough to determine whether a denarius, antoninianus, and proablty a siliqua, are within weight range tolerances, that's not accurate enough for me to include a weight in my attribution, not even as an estimate.
Sure, there will be variation across different scales, but I suspect most of this variation lies in the differing weights of the white inserts which are sized/milled to fit the particular coin and some variation in the larger clear plastic part of the holder.  After all, a 1/2 gram variation in items nominally weighing 40 grams is only a 1.25% variation.  But, if that variation leads to predicted coin weights with variations of up to 1/2 gram, in items nominally weighing 3-4 grams, the variation becomes roughly 12-16%.  Again, that's too much variance for me to accept this method of estimating weight and reporting it in an attribution.

Thanks for the responses guys.  I'd welcome the opinions of others.   

Offline PMah

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #5 on: June 22, 2022, 06:42:44 pm »
I would "subtract 100%" of the weight of the slab by freeing the coin.  (I use a dremel motor tool and a vise...)
   That's if the slab isn't adding much utility or value, both topics of dispute.  You can keep the info label if that helps re-sale, if resale is a priority.  I find slabs to be a high negative in most respects, including storing only 20 coins in space that would hold 100-150 and bearing nearly useless labeling that needs a taped-on tag for collection control, references and almost all other information I find useful.
   For the person with an unreliable scale, I suggest getting a calibration kit, which are not expensive and will remain useful if you decide to upgrade your scale in the future.  But you may find, with calibration,  your unreliable scale isn't so bad.
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Offline Virgil H

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #6 on: June 22, 2022, 07:35:02 pm »
Obviously, this is only an issue for people who like slabs. For my freed up slabbed coins, I did keep the NCG tag. I have no idea if that will help when I or my heirs sell them. I also find the info on their tags to be completely lacking to the point it is absurd. I get that some people like slabbed coins and that is a personal choice. I always think in my head that a slabbed coin is overpriced immediately because slabbing coins is not inexpensive, so I don't look for them. I have one coin that I got at auction that the slab had to have cost close to what I paid for the coin. Someone lost money on that one. And also made almost nothing on my other slabbed coin.

On the scales, I know the "unreliable" scales are generally fine. Calibration kits are not calibrated, so I don't hold much store in them, but mine came with a 10 gram "calibration" weight that seems to tell me my scale can weigh 10 grams accurately. And I know for my purposes, it is accurate enough. I was so programmed in the Army with everything needing to be so precision. We had second level resistance standards in a temp controlled oil bath that was checked four times a year against the national standards and we sweated doing those quarterly measurements and only certain people got to do them. And all scales were calibrated then and, yes, we could adjust them to make them read correctly if necessary, which could be a PITA to get consistency across a wide range that was always within tolerance. There is literally no way that a doctor's office scale measures completely accurately for everyone from small kids to obese adults. But, that probably doesn't matter as the accuracy is probably within reason.

The biggest problem with an unreliable scale is that most people don't know it is unreliable, which was kind of my point. It really depends on just how unreliable it may be. I fully realize that this is what we have today and I trust my gram scale enough for my coins, as well as my dog's medicine when I have to cut her pills that never cut cleanly, or measuring pink salt for curing meats. My kitchen scale is fine for cooking and weighing packages and my 60 year old analog postage scale is still pretty accurate from the tests I have done on it. Sorry, went on a big tangent here.

Cheers,
Virgil

Offline Ken W2

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #7 on: June 22, 2022, 08:52:58 pm »

Lol Paul. I am not a fan of slabbed coins either and was simply seeking a way to make  somewhat traditional attributions by including dimensions. I’ve broken a few coins out, but the higher value the coin the more value a third party authentication may have. I’ll never sell any of  my coins, but my children probably will and for better or worse they will likely find a more ready market at fair prices with third party authentication.  I also get some measure of confidence when buying slabbed coins of higher values. To be sure, third party authentication is not a guarantee of authenticity but it does provide an incremental measure of protection.  While we could break out all slabbed coins, save the packaging, and have a photographic record thereof, that is just that much more stuff for my kids to find, understand, and keep up with, in a subject matter they know little or nothing about. 
Thanks for responding. 














Offline Ron C2

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #8 on: June 25, 2022, 12:48:50 pm »
Slabbing ancient coins, for me, is just a way of getting a rather reliable opinion on authenticity. Every coin I ever had slabbed, got deslabbed upon return. I do keep the info slip with the coin.

There are different tiers of slabbing services and the cheaper tiers preserve less info on the slab slip.
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Offline Virgil H

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #9 on: June 25, 2022, 06:28:44 pm »
Ron, just curious, can't you get the service and not have them slab it? Paying for an opinion about a certain coin(s) I can see. Slabbing I do not want. But, an expert opinion is another thing.

Virgil

Offline Ron C2

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #10 on: June 26, 2022, 07:56:05 am »
Not that I know of. Slabbing is how they ensure you resell the coin they saw and not a copy of it.
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Offline Victor C

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #11 on: June 26, 2022, 10:46:24 am »
can't you get the service and not have them slab it?

If you are not familiar with him, David Sear offers authentication.

https://www.davidrsear.com/certification.html
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Offline Virgil H

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #12 on: June 26, 2022, 11:28:23 am »
Ron and Victor,

I understand that aspect of why coins are slabbed, I didn't know you could not opt out of getting it slabbed. I have always wondered if the deslabbed coins of mine where I retain the NCG tag will make any difference in selling. It really doesn't matter to me, but might to my heirs. I am familiar with David Sear and his services. Doesn't Wayne Sayles also offer such?

Thanks,
Virgil

Offline Ron C2

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Re: Cataloging Estimated Dimensions of Slabbed Coins
« Reply #13 on: June 26, 2022, 11:27:32 pm »
Sear does.  Not sure who all else does, in-hand, most of us can pretty reliably determine a fake without their help

In terms of slab slips, the original slips are hard-ish to fake, and it's unlikely a coin with the corresponding slab slip is a copy/fake of the coin that was originally slabbed.
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