Where do they come from? I'm not producing them, but more and more is showing up. I'm at 450 so far (81 years in).
Well, they can be crafted at the melting house, that'd be the clearest way to produce them, but you'd be aware you're doing that (I guess...).
You can randomly get some too in chests that are spawned right at the start of your game during map generation (like rocks and ore) and that will get cleared by your workers. You might not notice the chests unless you're really looking for them, but they'll get you some coins, or some healing oils or other semi-rare things.
They're also produced by some of the townhall-style buildings. I forgot the name (I'm currently playing with different mods), but one of the buildings says it taxes people. That tax generates silver pfennig.
