Coins maybe not, but ingots? Small ingots of metal were likely traded at this time, heck they've found stone in much earlier sites that's non native that likely would have been traded. People trade whatever's valuable.
Trick is how to put this into the economy.
- Shane
My idea was something like this, though originally I was testing a way to find the exact price of things by getting naked and holding only the coins while trading, then asking what they prefer (worked). The weights for gold and silver coins are based on the most ancient coins found from Persia. The idea is that you could work them into something valuable as well, but also have a "billet" or ingot form to be able to melt stuff into.
The weapons menu seem to havr enough space for some gold/silver/bronze weapons (with different values based on weapon type) but other objects could get the appropriate tagging if "X bloom" and "X ore piece" werr changed to "bloom of X", "ore of X", etc... as happens with fibres already. This would allow naming the item depending on the ore used.
The problem is that pricing these items differently would require commenting in/out a price tag. While simple and solving the space problem, it requires this manual action. But you could have a silver hammer or a golden pot!
This could be extended to other items like "Arrowhead of iron/silver/gold" used with [naming:last word]
The roasting and smelting can easily fit into the mining and and ironworking menus, I think.
I used the gold to silver ratio of 1 to 20 and about the same of silver to copper though it appears to have remained about 0.1 to 0.3 throughout history. The coin idea might need balancing to make it not broken and less valuable for the effort, resources and tools needed (don't forget that) but it could work with the idea of the metalworker in mind.
Also, bronze could be melted from bronze brooches and stuff, giving them a new purpose. Alternatively, we could mix iron and copper together to make bronze.
Edit: btw, copper, silver and gold do occur naturally, and I know there's deposits of gold in finland. Finding them should be hard, kinda balancing it out.
Edit: another option would be having a swappable menu with the bronze/etc crafting recipes