How are the sizes of coins determined?
cheezhed
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For example, ASE 1.598 inches (40.60 millimeters). Sizes like this seem odd or random to me. Is there any rhyme or reason to this?
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That’s a good question. I’m interested in knowing the answer too. I used to think it had something to do with the value of precious metals used for the coins when each denomination was first minted, but it would be easy to make them a little bit thicker and smaller in width or thinner and wider. I also read somewhere that Bechtler gold dollars often had to be pried out of the dies with pliers and they would end up bent or damaged because they were too thin, so something like that might have been involved in figuring out the minimum thickness.
Mr_Spud
This is what I know. Congress dictates the sizes of all coins. If I had to make a one word answer it would be "precedent". There are certain sizes that have been used for many, many years. You have things like the vending machine companies who would need consistency. I have several blind friends. Again, they need consistency in order to function. I would guess determining production costs and what not are also easier if you don't have to compare apples to oranges. As far as items like the AES and what not they probably have to compete with other international producers and again consistency and precedent rule the day. Just my thoughts. James
Volumetrics and design.
The law says 1 troy ounce and 40.6mm in diameter. Those two dimensions dictate the average thickness.
https://www.congress.gov/99/statute/STATUTE-99/STATUTE-99-Pg113.pdf
ANA 50 year/Life Member (now "Emeritus")
@BStrauss3 summed it up. The ASE could have been standard at 38mm but then it would have been almost 1/4 inch thick and we’d be pondering a different question.
I’m actually any astute collector would be confused about this.
"Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety," --- Benjamin Franklin
Whatever fits into the vending machine.
It has to do with the coin’s composition and influences from other nations’ coins. For example, a silver dollar was similar to the silver crown coins that other countries were issuing. The early $5 gold coin, which had too much gold in it, was similar to the British gold guinea. That excess gold resulted in many of them going to the melting pot. It got much worse when the British reformed their coinage and switched to the lighter weight sovereign.
In more modern times, some foreign visitors wondered why the dime was smaller than the nickel. The answer was the dime was originally made of silver.
As the ASE, I’m very glad that it is the size it is. Coins which are too thick, just coins, which are too thin, are not easy to handle. The ASE is a bullion trade coin. It was only given a face value of one dollar because it allowed it to get around sales tax laws in some states. Coins have often been treated differently than pieces of bullion.
Canadian silver maple leafs are 38mm.
I read something long ago that said that the early Mint had a preferred ratio of thickness to diameter that it tried to stick to, once the diameters were largely set in stone during the 1836-1840 period. Don't know what that ratio would be, and I assume that once a diameter was determined this way it was "tweaked" so that the diameter would be an even fraction or multiple of an inch, for ease in measuring collars and planchets and etc.
I also don't know if this ratio was calculated using the diameter and thickness of a blank or a struck coin, which is of course thicker at the rim than a blank.
Once the diameters were more or less set in stone circa 1840, the ratio for blanks would have been thrown off for the fractional silver once the thickness of the blanks was reduced by about 7% in 1853. Of course, they might have raised the heights of the rims on the struck coins to keep the overall thickness of the coins constant.
And of course the OP's question was about a modern coin, the silver eagle. I have no idea why the diameter used for that was selected, but I do know that the diameter for the Susan B. Anthony dollar was chosen specifically because there was no common, low value foreign coin of that exact diameter, thickness and weight in existence that could pass as a U.S. dollar in a U.S. vending machine. The Mint had great hopes that the SBA's were going to be heavily used in vending machines, and they tried very hard to make it happen.
TD
1836-1840 aligns with the introduction of the steam-powered press / retirement of the screw press. This allowed much higher pressure to be applied during the striking of the coins and thus higher relief.
Higher relief means the rims have to be higher so the coins stack.
Coin-operated vending machines arrive in the 1880s and that cements things until the present.
ANA 50 year/Life Member (now "Emeritus")
US silver (or at least formerly-silver) denominations - specifically the quarter, half, and silver dollar - are all essentially based on the measurements of the Spanish 2, 4 and 8 reales coins. Which of course simply kicks the can down the road: why did the Spanish make their coins those specific sizes?
Spanish dollars and their fractions were originally very crudely shaped (so-called "cob" coins) with their weight, rather than diameter, being the critical measurement; the diameters eventually chosen once the coins became machine-struck (and therefore nice and round) were essentially a trial-and-error evolution in terms of "what diameter works best for a silver coin with this weight". What this magic number was, varied from mint to mint; mainland Spanish 2 reales coins were typically around 26mm, colonial-Spanish coins more typically around 28mm.
US coin measurements were originally based off of the typical worn-from-heavy-circulation Spanish coins found in revolutionary America. These measurements then evolved separately from their Spanish prototypes, according to the whims and dictates of the US government of the day.
The coins which don't have this Spanish heritage - the cent, nickel, and dime - have dimensions which were all somewhat arbitrarily chosen, but they all tend to gravitate towards a similar diameter-to-thickness ratio. If coins are too much thinner than this, they become easily bent and broken, not to mention become susceptible to ghosting and other engineering drawbacks when it comes to trying to make them using high-speed modern coin presses. If a coin is too thick, it becomes unwieldy, and hard to manipulate in terms of piling them up into a stack or using them in a vending machine.
Roman emperor Marcus Aurelius, "Meditations"
Apparently I have been awarded the DPOTD twice.
Via a coin flip, of course
Non-pvc, I hope!
Just intuitively I can't picture such a small reduction in diameter nearly doubling the thickness.
At 38mm the thickness would be a little over 1/8 inch, so I exxagerated a little but I think you understand my point.
"Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety," --- Benjamin Franklin
We know somebody who failed geometry in high school. Volume of a cylinder is (pi) * r^2 * h
The difference between 38mm (19mm r) and 40.6mm (20.3mm r) is 6%
ANA 50 year/Life Member (now "Emeritus")
Originally? Factors like required weight and practical thickness, borne out through experience, eventually normalizing through shared cultures. There. Now you know.
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