This is a niche topic to be sure so I want to start with some background information.
The story we've all been told about the history of money is a disproven lie. we didn't start with barter, commonly agreed upon commodities did not emerge from it as the first forms of money, representative money did not emerge from that, and fiat money did not emerge from that.
debt and credit and virtual money came first. only with the rise of large armies did coins come about and they had values tied to the power structures which issued them not their gold or silver content (coins circulated at much higher values within ther borders than outside them where they were simple the value of the metal inside them). they were made of precious metal so they would be hard to copy. Roman coins were incredibly varied in weights and sizes so any notion of them being anything but tokens is illogical (you can't have the coins be an average value of their weight in gold since anything coin with twice as much gold as another which is said to be worth the same would be melted down. unless both were worth more than their content).
After the collapse of the western roman empire the feudal powers continued to use roman coins NOT physically but just virtually on pen and paper as units of account. this lasted until Charlemagne when Carolingian money came into being which was literally referred to at the time as "imaginary money". Many of the Carolingian coins (pounds and shillings and pence, etc) existed either for incredibly short times in incredibly short supply or not at all (Charlemagne never actually struck even a single silver pound).
All that being said, there was something which was called "crying up" or "crying down" a currency. The king or lord or whoever would declare a new exchange rate between pounds and shillings or pence and pounds as a way of raising taxes. Many people seem to think this was a physical re-issuing of the currency where the king would issue new coins with less silver or gold in them. This was not the case. Physical coins were recalled and redone sometimes (and as further proof that the coins were token, the economy didn't cease to function since it was the units not the physical objects people were using to trade) but that was different. Credits and debts would be measured in pounds, shillings, pence, etc. separately and upon declaring a new exchange rate either some debts would be reduced or some credits reduced or increased or what have you.
for example, "crying down" would be a de facto tax increase. in instead of 20 shillings per pound there were now 30, then any tax of 1 pound would be 1.5x higher. "crying up" was the opposite. if the king had 1 pound of debt, he could redeclare 1 pound to be 10 shillings instead and suddenly his only owed half as much.
If anyone has any sources detailing some episodes or policies of such crying-up and crying-down of currencies please post them.
I have (after some searching) found a resource!
The History of Currency, 1252 to 1894: Being an Account of the Gold and Silver Moneys and Monetary Standards of Europe and America
have not read it but I thought I'd leave it here for anyone interested.
I've been wondering why the seemingly arbitrary exchange rates between pounds, shillings and pence. This helps explain that.
it seems like the ones that stuck were nice in that they were easily divisible. the thing that it explains the most to me is why have different units to begin with.
why not just measure everything in pence or everything in pounds with decimals/fractions? well, if you've basically got 3 parallel coins, 3 parallel media of exchange, and 3 parallel units of account you can do some real fuckery (pardon my french) as a financier.
I've been reading the text I mention and (tho it is dated) it's very eye opening. it seems like international finance has been with us for basically all of written history but especially in post-roman europe. english and french and spanish kings are crying up and down their currencies seemingly every season to get the silver or gold to flow toward their country. they adjust them as often and as passively as our modern central banks do with their interest rates.
post script:
to the point of international finance being very old. the english word "cash" comes ultimately from Tamil word for Chinese money. "Check" is an arabic word (meaning check) which comes from a time when almost every transaction across the muslim world was done via personal checks.