Just to show how much I care…I did research on numismatics for you, and that’s something I once swore I would never do. 

Medieval coins were “cold-struck” which means that the planchet or blank were allowed to cool before they were imprinted. They were made by hand, by sticking a planchet in between two dies (the one on top called the trussel die, and the bottom die called the pile die) upon which the design of the coin had been engraved and then hitting the trussel die with a hammer to imprint the planchet with both the obverse and design side at the same time. 

The coining was actually the simplest part of the process. Producing the dies took up a lot of time, because the action of smacking them with a hammer inevitably damaged them – to take the Venetian mint as an example, they had to make one trussel die every day and one pile die every other day, because when you’re punching out 20,000 coins a day, the dies are going to get damaged in a hurry. Making the blanks was also a rather complicated process and took up a huge amount of time: 

1. melting and casting the ingots,
2. annealing, or heat treating, the ingots to soften them,
3. hammering the ingots,
4. another annealing,
5. cutting the ingots into blanks,
6. annealing the blanks,
7. hammering the blanks thinner,
8. another annealing,
9. another hammering of the blanks,
10. another annealing,
11. another hammering of the blanks,
12. rolling and
13. hammering the edges to make the blanks rounder,
14. another annealing,
15. blanching to clean the blanks
16. and then finally coining.

In terms of how often the coins were made and why…part of it had to do with custom: new coins would be minted to celebrate the coronation of a new monarch in order to spread the word about who the new monarch was, new coins would also be minted to celebrate major military victories or weddings or the birth of royal children, or certain religious holidays. But a good bit of it had to do with supply and demand: i.e, when the monarch needs cash to buy stuff or when various vendors bring in royal ious and request payment in cash or when the royal paymasters need to make payroll for the army or the navy, etc. 

Speaking of supply and demand, one of the long-term problems with metallic currency is that, over time, they have a deflationary bias – as people hoard coins, money falls out of the system, and prices start to drop in ways that become very dangerous to profit margins and thus economic viability. Thus, you have to mint coins just to make sure that there’s enough coins going around for economic transactions to take place and for the economy to grow. And the problems don’t end there: because metallic coins are easily counterfeited by clipping or sweating or plating, mints were constantly battling Gresham’s Law, which is one of the reasons why medieval punishments for forgery and counterfeiting were so legendarily brutal. 

Ultimately it came down to how well things were going for the state. Remember, the coins are made of precious metals, which means you need the raw stuff on hand to mint. When things are going well economically and politically – trade is flowing, the harvest is good, people are paying their taxes – the king mints lots of coins both because he can and to show off his royal splendor and majesty. But when things are going bad – when the harvest fails, trade dries up, people are refusing to pay their taxes, foreign armies are rampaging up and down the countryside stealing everything shiny – first you start to adulterate your coinage with baser metals, then you cheat on the weight of the coinage, then you just stop issuing coins for a while. One of the ways that historians of the ancient world or the medieval period try to assess the strength and stability of various dynasties is just by looking at how frequently coins are being minted, how the weight and purity of the coinage is changing,