Questions about measuring coins

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What is the correct way to measure thickness? Is it the edge of the coin where there is some uniformity all around, or is it across the whole coin including the highest design elements?

What is the diameter of an ancient coin with less uniform edges than newer ones? Is it an average, or the largest number, or from any particular place to place?

Are there rules to maintain as much consistency as possible?

Thanks!
I asked the same question about thickness on the Referees part of the forum. The answer is there is no proper definition; thus, I believe measuring at the rim is the best option.

As for diameter of ancient coins with non-uniform flans, I use the Coin Size Chart in an old Krause catalog, and I look for the size which contains at least 90% of the coin (that's just my way of doing it). I also keep in mind the diameter listed in the Numista catalog is supposed to be for the type, not an individual coin.
I can repeat my comment from that topic on the Referees forum:

I think that thickness can be defined as a dimension of a cylindrical container that can be used to store this coin. So if a coin is thicker at the rim, you should measure it at the rim. And if it's thicker in the center, you should measure it in the center.

So measure it everywhere and find the biggest number.
Quote: "ciscoins"​I can repeat my comment from that topic on the Referees forum:

​I think that thickness can be defined as a dimension of a cylindrical container that can be used to store this coin. So if a coin is thicker at the rim, you should measure it at the rim. And if it's thicker in the center, you should measure it in the center.

​So measure it everywhere and find the biggest number.
​I find it hard to believe there are any circulation coins which have the highest point in the center; other than perhaps an odd ancient. That's because a lot of engineering goes into the design to make sure coins stack well. Does anyone have an example other than an odd commemorative such as the US Baseball Hall of Fame coin?
You are right. The design of the current coins should be thicker at the rim. Medals and ancient coins may have a higher thick in another point than rim.
Quote: "Steve27"​​I find it hard to believe there are any circulation coins which have the highest point in the center; other than perhaps an odd ancient. That's because a lot of engineering goes into the design to make sure coins stack well. Does anyone have an example other than an odd commemorative such as the US Baseball Hall of Fame coin?

​The definition must take into account all possible cases. Yes, perhaps, on modern coins the rim is usually thicker than the other elements, but it should not affect the general definition.

If I'm not mistaken, Peruvian 1/2 and 1 sol have the central image higher than the rim. Also Brazilian centavos of 1940s-1950s with high relief portraits.
Even high relief coins will have rims which are taller than the central devices.
Hammered coins (no mechanical/hand struck coins) are almost impossible to mesure properly.
They're all different!
Cents are money too!
I would like to see "thickness" dropped from the coin listings on this site. It's usually not available from the mints who produced the coins; thus it just leads to confusion and provides no added information to the collector.
Quote: "Steve27"​I would like to see "thickness" dropped from the coin listings on this site. It's usually not available from the mints who produced the coins; thus it just leads to confusion and provides no added information to the collector.
I can't agree with that. Thickness is an important feature to distinguish between subtypes of coins. And if you personally don't trust in the methods of measurement - that is only your problem. Don't try to destroy what you didn't create.
Additionally, another reason to delete it, is that there are many which are incorrect. Such as this one: https://en.numista.com/catalogue/pieces6847.html
Quote: "Steve27"​Additionally, another reason to delete it, is that there are many which are incorrect. Such as this one: https://en.numista.com/catalogue/pieces6847.html
​and what is the right thickness of this type?

Yes, many measures are wrong, because used and sometimes damaged coins were measured or a plastic caliper were used.
But the thickness is a very important information for me.
If i see a missing or wrong thickness, i make a change request.
Ideally, we should give thickness only from UNC coins. The rim get rapidly worn.

As for older hammered coins, measures are very variable. I usually give the largest diameter but for irregular coins, it is not precise. But it gives an idea.
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Quote: "Handzumgrus"
Quote: "Steve27"​Additionally, another reason to delete it, is that there are many which are incorrect. Such as this one: https://en.numista.com/catalogue/pieces6847.html
​​
​​and what is the right thickness of this type?

​Yes, many measures are wrong, because used and sometimes damaged coins were measured or a plastic caliper were used.
​But the thickness is a very important information for me.
​If i see a missing or wrong thickness, i make a change request.
​The problem is, there is no accepted text providing the information, and it's difficult to estimate when you've seen one but don't own one. In this case, the value used is probably twice what it should be.
Quote: "Ecapoe"​Ideally, we should give thickness only from UNC coins. The rim get rapidly worn.

​I collect coins by years, so I measure many coins of each type and subtype. Some of them are UNC, and the others - XF, VF or even F. And I can tell you that only in very few cases there's some correlation between grade and thickness. Normally, the thickness of the coins of each subtype is a range of numbers, and UNC coins may be in the middle of that range or sometimes the thinnest of all.

Ideally, we should give not a single number but a range of numbers.

By the way, diameters and weights also vary in each subtype and also don't correlate with the grade; for them it's also necessary to provide a range of numbers.
Quote: "ciscoins"
Quote: "Ecapoe"​Ideally, we should give thickness only from UNC coins. The rim get rapidly worn.

​​I collect coins by years, so I measure many coins of each type and subtype. Some of them are UNC, and the others - XF, VF or even F. And I can tell you that only in very few cases there's some correlation between grade and thickness. Normally, the thickness of the coins of each subtype is a range of numbers, and UNC coins may be in the middle of that range or sometimes the thinnest of all.

​Ideally, we should give not a single number but a range of numbers.

​By the way, diameters and weights also vary in each subtype and also don't correlate with the grade; for them it's also necessary to provide a range of numbers.
So we should write in the coin sheet the official diameter, weight and thickness (if we can get this informations) and the measured parameters with range in separate fields.
I would be happy.
Now we have one field and there is written an official information or a measured information or redicoulus rubbish because of lack of good measuring tools.

I would say we need an additional field for each parameter.
Measurement of coins are in the description to help us to determine which coin is it in certain cases (sometimes variants are only for weight or dimensions); and also to let us know about how the coin should be like.

For my country, I am lucky from several years ago, every one have a law nr. to be issued, and there is the description of the coin, as it should be; they also stats a (very small) tolerance on the final dimensions and weight of the coins; if they are out of the range, they are rejected. Therefore, there is an oficial size and weight for them.

On the other hand, the rim is intended to give stability when you stack coins, but of course there are exceptions as mentioned, usually the rim thickness is the maximum of the coin, so should be the one to give. If you don't have official measures, would be a good idea to stack several coins in the best conditions possible, like 5 to 10 coins, measure them altogether and calculate average of each. Same with weight, taking from several and averaged should be very close to original one.

Please keep in mind, when you search a coin at Numista, will list a range of +/- 5% (explained at the (?) besides those boxes), or if you think could be a greater difference, you can put a range (like 7-12g) to expand your search.
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