How was currency converted in the middle ages?

Question

I have tried to look for an answer using the [currency] tag but none of those questions had answers that sufficed.

I understand that back then there were a myriad of currencies, most of these were based on silver and gold, and their value in said ore usually represented their denominated value as well. (at least this is what I assume, correct me if I am wrong).

At some later point the denominations value was provided by an other backing aside of what the actual coin was worth, but my question is more about when a gold coin's worth was governed by the gold that was used to smith it.

example

Say there are two kingdoms, each mint gold coins. Crowns and Florins as an easy example. Trade is plenty between said kingdoms so there have to be conversions of the currency going on.

Now if the currencies have different shapes and thickness I assume one coin type would be worth more than the other, if looking at the metal value. How is this difference in worth handled by the converters? I read a lot about using scales and we all know the stereotypical image of somebody biting a coin to check if it is fake, but this can't be how it was done surely?

Additionally, how can they check if a coin had a core of another metal (of less worth) but a coat of gold?

And for the kingdoms, how could they be sure their coinage was not devalued? I could think of some tactics to weaken a kingdom by tampering with their currency. Chaffing gold off their coins, forging them with a lower gold content and trading them out to melt their actual coins, and so on. These are things I come up with and I have little knowledge about it. I guess somebody with more extensive metallurgical knowledge can think of plenty more things to do.

Summarised questions

• How did they make conversions between two currencies in the middle ages (and other appropriate times) with currencies which's denominations values were the actual metal value of the minted coin? (backed by the metal and not the state or something)
• How did the converters handle forgeries and tampering with the coin?
• How did the kingdoms/ empires/ ... handle their currency being tampered with and exploited? Did this happen at all?

Answer 1

The metal value of gold and silver was the basis of their value, so if you didn't know the coin, you would simply weigh it on a scale. If you knew and trusted the coin, you might accept it at its known value.

There were, however, numerous ways to cheat. One was to clip or shave coins by cutting small pieces off the edge of generally accepted coins and later use the shavings to make new coins, gold rings or whatever. Making ridges on the edges of coins was used to combat this practice.

Some states that were low on gold mixed the gold with cheaper silver or lead while pretending that the coins were still pure gold. This debasement was hard to detect unless you measured both the volume and mass of the coin. A more extreme version of this was to just plate the baser metal with gold; something that you could detect by cutting a coin in half.

It is important to note that most people in the Middle Ages didn't use coins, but just bartered their goods. Especially gold coins were so valuable that it made sense to test their authenticity.

Answer 2

The relative weights of the coins would have been known so 7 florins = 13 crowns or whatever. If the coins were not recognised they would not have been accepted. The coins themselves with the official stamp would have provided a degree of surety that the coin was in fact made of gold. It would have been difficult to insert anything into a thin coin using the technology of the middle ages. Some people tried to cut the edges off so weighing coins might have been a useful check.

Tampering with currency by the government of the day has been going on since antiquity and many Roman emperors did so in fact it goes on to this very day by way of inflation and huge unpayable debts.

Answer 3

What mattered was how much gold/silver the coins had. There are techniques to measure that but I can't remember exactly what these techniques were right now. It a coin had less precious metals then the other it would be worth less. So they measured the precious metal amount.