Coins

sjmiller

Explorer
Okay, bear with me, this really does have something to do with RPGs. I am working with a friend creating his game world. He came to me with some questions about coins, and I am stuck, so I came here.

I have some information on the materials used to make a coin, the diameter of the coin, and how many coins are in a pound. What I want to know is how thick the coin needs to be. Let me give a couple of examples.

The crown is a coin made of gold, approximately the same size as a current US dollar coin (26.5 mm diameter), and there are 50 coins per pound.

The sovereign is a platinum coin, approximately 38.1 mm in diameter, and there are 12 per pound.

So, what sort of formulas would I need to use in order to figure out how thick they are? I used to have all sorts of things like this written in a book, but the book suffered damage recently.

Thanks for the help folks, I appreciate it.
 

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Basically you just need to use density data for the metals

Gold = 19.3 g/cc
Platinum = 21.4 g/cc

And your weight information to find out how much volume is needed to get the weights you listed. Then volume/area = thickness. Area = pi*r^2

For absolutely pure metals (which wouldn't really happen) the gold coins would be 4.7 mm thick and the platinum coins would be a whopping 17.7 mm thick.

Edit: Ignore me, I forgot a step :o
 
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I figured it out once for D&D using the 50 coins per pound. A GP would be about the size of a penny (but weigh three times as much) which is very close to historical sizes of gold coins from Roman times. Platinium piece would be about the size of dime. Silver piece would be about the size of a quarter. Copper piece would be about the size of a quarter but thicker.

However, in general: Find the density of the metal you want to use. Assume one pound to find volume and then divide by number of coins per pound. Take the volume of the coin in question and divide by PIr^2 and you have the thickness.

Edited to add:

gold = 19.3 g/cm^3
1000g = 2.2046#
V=T*PI*r^2
50 coins/#
D=2.65cm

Find density of gold in # per cm^3
(19.3 g/cm^3)(2.2046/1000 #/g) = .042548 #/cm^3

Multiply by 50 coins per #
(.042548 #/cm^3)(50 coin/#) = 2.127 coin/cm^3

Find reciprocle(sp?) for volume of each coin
.47 cm^3/coin

Solve for thickeness of coinusing volume of disk where volume and diameter are known
T = V/(PIr^2) = v/5.5126625 cm^3/cm^2 = .47/5.52126625 cm = .0853 cm

So, a gold coin of the diameter you state will be less than a millimeter thick.


For plat

Platinum = 21.4 g/cc
1000g = 2.2046#
V=T*PI*r^2
12 coins/#
D=3.81cm

Find density of gold in # per cm^3
(21.4 g/cm^3)(2.2046/1000 #/g) = .04717 #/cm^3

Multiply by 12 coins per #
(.04717 #/cm^3)(12 coin/#) = .566 coin/cm^3

Find reciprocle(sp?) for volume of each coin
1.766 cm^3/coin

Solve for thickeness of coinusing volume of disk where volume and diameter are known
T = V/(PIr^2) = 1.766/PI*3.629 cm^3/cm^2 = .155 cm

So, your plat are looking at being a milimeter and half thick.
 
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All my copper, silver, and (one) gold roman coins are all very close in size. Having platinum coins being so huge is very impractical. You would darn near be better off carrying the gold coins.

I would have the platinum coins be the same size as the gold. Besides, it has been a couple of decades (late 70's, early 80's?) since platinum has been worth five times as much as gold anyways. So a "realistic" relation of value and size sure isn't needed. Plus it isn't as if Platinum was ever widely used as a coin in real life anyways, except for maybe special collector mintings.

Any coin experts/collectors want to educate me?

Edit: Besides, there are over a 100 roman gold coins per pound in real life. So if reality is something you want you need to make it a 100 coins/pound instead of 50 anyways. Plus the old roman coins are nothing close to being exact copies of one another like they are today. Rough edges, off center marks, etc... Plus the whole reason coins even have ridges is to cut down on the practice of literally shaving the coins, back when they were pure silver and gold. Pure for their purposes anyhow. That convention is no longer necessary since coins are far from pure silver, or gold.
 
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Well, I talked with Jon today, trying to tell him his coin sizes are off. I showed him this stuff, and the 8 or 10 books I have on Roman and Medieval coins. He finally told me that he's basing the coins off of the old Judge's Guild book The City State of the Invincible Overlord. Two of the coins there are the ones I mentioned. The others are all the diameter of the Crown, but are silver, copper, and bronze. I told him the number per pound is too small, but he said that is what he wanted to use. So, the silver coin is going to be 50 per pound, and the copper 25, or is it the other way around? I can't remember.

Anyway, a 1 mm thick coin of that diameter in gold is going to get bent a lot, don't you think?
 

Yeah, I think the roman coins average about 3 mm in thickness. If he is doing CSIO the Overlord is the law and what he says goes, no matter how much it may be questionable.
 

How I handle coins in-game:

1 gp = 10 sp = 100 bp = 1000 cp. The bp is a bronze piece. The standard coin will be the silver piece. All costs in official 3.5E sources should be read as sp when it states gp. There are 32 coins to a pound. Each is roughly nickel sized.

The Elven Kingdoms use an electrum ring as currency. Each is worth 5 silver pieces. They are commonly worn as rings or strung on a cord and worn as bracelets or necklaces. Among poorer human populations they are becoming common as wedding bands.

Dwarves frequently use mithril ingots as currency. The usual sizes are 5 sp, 25 sp and 125 sp in value.
 

sjmiller said:
Anyway, a 1 mm thick coin of that diameter in gold is going to get bent a lot, don't you think?

You can always say the gold isn't pure gold, but some handwaved alloy that's strong enough. Or maybe in the minting process, they're alchemically treated for strength (and maybe anti-counterfeiting measures).
 

gold does not need much of other metals to make a strong coin alloy.

Moneyer and money

Now in the D&D world we have moneychangers. But how come no world has a moneyer? I have yet to see a profession list which does have a moneyer on it. Now we still have moneychangers today. Just go to some cities, which have international tourists. In Berlin, you could change dollars to, east marks, west marks, pounds, francs, and rubles. So exchanging that new found old money in for current city state coin is old hat for your average party, if the DM even worries about it.
But what is a moneyer? What does he do? How can you fit the position in your game?

A moneyer is expert craftsman who job is to create new coins from old or new coins from bullion. Other names for moneyer are coiner, and minter. The job has two parts, making the die and stamping and or casting the coin.

The die making process is very simple just requiring some blacksmithing and engraving skill. The basic process with some variation is as follows. First two rods are forge about six inches long. Polish smooth and flat one end of rod. Using small punches and other tools engrave and punch the design obverse (heads) into smooth polish edge. Repeat for reverse (tails) rod. Heat treat and temper design ends of the rods. The result is the working dies. The dies do not have to always be two rods with the reverse stuck into a hole in a stump. Some die of reverse could be a square chuck of metal with spike tail which is place in the hardy hole of anvils or drove into a stump. The face of square would have the design in center.
Dies depending on the country and time were limited in where they could be manufactured. However money could be minted in various locals. For example to change the current process of today in the United States the plates would be created at the mint but the regional federal banks would print dollars at their location. So in my neck of the woods the plates would be created in D.C. and shipped to Atlanta Ga. When the Atlanta bank needed more dollars, they would print their own.
Coin making process is simple but long. Old coins or bullion is collected and the amount received is noted. The coins and bullion are melted. The molten metal is poured in sheet forms. The sheet is cut into strips. Then using a punch or large snips the planchet is cut. Think of the planchet as token or slug. The planchet is then stamped. Since the die was generally oversized, the coin is trimmed. Think of the oversize like a penny is bigger than a dime, so the dies would be penny sized and coin trimmed down to dime size. The coin is weighted. More trimming may take place. If the coin weight was too low back, the coin goes back in melting pot. However not each individual piece was not generally weighted but it could be. Also various laws and tradition require the final product to be assay, however except for the annual Trail of Pyx, the coins were rarely assayed. The process was the same irregardless of the metal (silver or gold) struck.

The new coins, minus the moneyer’s cut and king’s cut, are return to the customer. The average percentage for the moneyer in England was six coins per pound or about one percent. The king’s cut varied but about six pennies per pound weight was the average. The money from moneyer’s cut had pay salaries and materials but generally was enough to be very profitable.

Some countries and people including the Celts cast their coins. I have not done any research on how the molds were made. However some planchets were cast in reusable molds. Take heavy duty crucible fill with scrap gold. Heat the crucible to pouring temperature, which is above the degree just to get the material to melt. Pour the liquid gold into a two part mold (think a fish sinker or bullet mold). Let cool. Open mold. Cut off flashing and return flashing to pot. Give planchet to striker.

Coins stayed in circulation long pass the time they were due to be turned in for reissue since the holder would lose face value due to debasing of coinage. Coins became worn either by normal wear or clipping. Clipping is not what gets your team a ten yard penalty during the Super Bowl. Clipping when it relates to coins is snipping a small amount from the coin. If you clip enough coins you can melt the scraps into bullion. Clipping can be stop in various ways. Laws stating if certain words or designs are not whole then the coin is not worth face value. Rimming is another way. Look at United States penny, on the face is Lincoln and the words In God we trust, Liberty, and the year. On the reverse of the penny are the Lincoln Memorial and the words United States of America, one cent. King George Washington could pass a law stating if letters of wording is not whole merchants can not accept the coin. The penalty for clipping if found guilty was generally hanging. Rimming is best shown by looking at the edge of United States quarter or dime. The ridges are the rimming. Words have also been used for rimming. Debasing is the reason Henry the VIII was nickname ‘Old Copper nose’, when on the third coinage of his money he lessen the silver content. So high relief areas like the nose wore quicker to show the copper base.

You can use a moneyer in your campaign by reflecting modern times. You can’t buy a soft drink in downtown New York with Japanese Yen. So have each nation, or city state create its own coinage. To keep with the PH, we will assume all moneyers make coins the same size in PH. Now when Bucky the Wonder Paladin goes to buy flowers for Sue Succubus in the Greyhawk city; he either is not going to get lucky that night. Or be fined for passing funny money.

Coin craft’s English and UK coins 1066 to Date www.coincraft.com
America’s Money America’s story by Richard Doty.
Coins and minting by Denis cooper note shire album version is abridge version of his original book The Art and craft of coin making: a history of minting technology
Notes on the Organization of Minting in Medieval England (taken from Challis: History of the Royal Mint, 1992)
http://www.fordham.edu/halsall/source/925edgar-coinregs.html Medieval Source book Edward the Elder: Coinage Regulations, C 902-925
Aethelred Unraedy: the Laws of London, 978

http://www.ananova.com/news/story/sm_871209.html rare coin for a mystery roman emperor who ruled Britain Emperor Domitianus coin was found in a find of 5,000 coins
 

Good write up, but I have jeweler/goldsmiths make the minting dies. So yeah, there is an official position for being a minter of the nations coin, but any competent jeweler/goldsmith can make the die.
 

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