NOTE: I went down the Wikipedia rabbit hole on this one – Wikipedia or a regular Encyclopedia is good for that when I find something I want to learn more about. Short version, there would be about 100 Roman gold Solidi in a US pound. In the early Roman empire the standard silver coin, the Denarius was a day’s wage for an unskilled laborer. A system where silver is the standard coin of trade would require one to determine how much that would buy and what the fractions of a silver piece, i.e. copper pieces, would buy.
This was mentioned in the past week and has come up on various RPG blogs over the years. Gold as the main coin is the default in AD&D. The weight of the coins is ten to the pound, which would be huge coins.
I was reading up on ancient Roman coins last week on Wikipedia, and the Romans used 72 coins to the pound of gold, for the Solidus. Another gold coin, the Aureus, was valued at 25 silver denarii, and its mass in relation to the Roman pound went from 1/45 under Nero (7.3 g) to 1/50 under Caracalla. The Solidus was a new coin under Diocletian and started at 1/60 of a Roman pound and equal to 1,000 denarii, under Constantine it had the 1/72 pound and was worth 275,000 of the massively debased denarii. In later years the Solidus equaled 4.6 MILLION denarii. The aureus was about the same size as a denarius, but weighed more due to the higher density of gold. They had copper and bronze coins that were common, but were debased just as severely as the denarius. This example shows that the price sheet in AD&D or other FRPGs is a snapshot in time, and as the economy is flooded with loot, prices should go up, if you want to model reality that closely.
The fantasy vs. reality, is that in the real world it is estimated that all the gold ever mined would make a cube of almost 21 meters on a side. The pile of loot Smaug has and other depictions of dragons has could not all be gold, based on the real world. Silver is another matter, I found this graphic that illustrates the amount of various sizes and weights of gold and silver and compares the size of all the gold every mined vs. all the silver ever mined. The ratio of gold mined to silver mined is 1:10.48 in modern times. Prior to current methods the ratio was about 1:8.52, and historically 1 ounce of gold has had the power to purchase 15 ounces of gold. Now, as of March, 2014, an ounce of gold is valued at over 64 ounces of silver.
However, in the ancient world, the silver coin was the standard. It was a day’s wages for an unskilled laborer. What I found interesting, is the for Roman soldiers, their annual pay in the Republic was 112.5 denarii per year, and was raised to 225 denarii a year by Julius Caesar; and they had to pay for their own food and arms. Centurians’ pay varied under Augustus from 3,750 denarii and the highest ranking, 15,000 denarii a year.
Depending on which era’s size and value of coin you wish to use in your game, or make your own standard; you can greatly vary the number of coins and the amount of wealth a single person can carry. In AD&D 1,000 coins weighs 100 pounds. A roll of quarters contains 40 quarters and weight 8 ounces, or 80 quarters to the pound. That would make 1,000 quarters weigh 12.5 pounds. Based on a modern pound, with 16 ounces, being 453.592 grams, or 28.3495 grams to the ounce, and a Roman pound being 328.9 grams with 12 ounces, each 27.4083 grams. This makes the Roman pound 72.5% of the modern pound, meaning that 1,000 quarter would weigh 17.24 Roman pounds. Similarly, a gold solidus would be 1/100 (1/100.798) of a US pound. With 100 gold solidi in a US pound, 1,000 of them would only be 10 pounds. Thus it would take 10,000 coins of this size to equal 100 pounds. This makes the ability to carry a large number of coins and large amount of wealth somewhat easier. Gems and jewels would still be a more compact means of carrying a large amount of wealth great distances.
A quarter has a diameter of 24.26 mm and is 5.67 g. Based on Roman coins of about the same era, both the Aureus 7 g and Solidus 4.5 g gold coins were about 20 mm. The Denarius was about 19mm and was about 3g, about the size of a penny – 19.05 mm and 2.5 g. The sestertius was about 35 mm and 20.3 g. A half dollar is 30.61 mm and 11.34 grams. The Eisenhower “silver” dollar is 38.5 mm and 22.7 g with a copper core and a copper/nickel cladding. A Morgan silver dollar is 38.1 mm and 26.73 g, so 0.4 mm smaller but just over 4 grams more massive, thus the heft if you pick up a “silver” dollar and a silver dollar.
BTW – The Troy pound is 373.241 grams with 12 ounces, Troy weight is used for precious metals. This is why a pound of feathers weighs more than a pound of gold if each is measured with their usual method and not on the same standard.
I have played in games with the default AD&D coinage system, and games with a silver standard of ten silver to one gold and ten copper to one silver and platinum and electrum are rare or non-existent, having only been used by the ancients.
My current game uses this silver standard with ten silver to a gold and ten copper to a silver. However, I have been re-thinking that. Yes, it is easy and decimalization makes the math easy. However, I am thinking about a new silver standard with 1 gold = 100 silver and 1 copper = 100 silver. That makes the copper nearly worthless, so maybe more like 50 silver in a gold and 20 copper in a silver.
Something to think about.
With 1 silver = to a day’s wage for an unskilled laborer, the value of a copper would need to be a reasonable breakdown of that. How many loaves of bread can that buy? Can a single silver buy enough to feed a family? How big of a family? A family of four, six, bigger?
The drawback to fiddling with the money system, is that you have to revise the price sheet to accurately reflect the new prices. Without a quick way, like a spreadsheet to fiddle with the relative value of each coin to the other, it becomes tedium.
[EDIT 11/16/2014 – Removed last line to remove incorrect information and a very confusing sentence.]