Currency in this game is really interesting but It has several issues that happen every world. These are:
Low-level currencies - tin, copper, iron coins etc - Hold no value and often pose as a risk for joining a market as a trader early. Trust comes at a premium and is often abused.
High-level currencies - Gold, Silver - Often used to solve the issue of low currencies but fall prey to inflation as the world goes on, the prices also continue to be established by shifting gold and silver prices and there are not enough sinks.
Solution
When crafting coins allow the players to "back" the currency with experience.
Soft metals 100xp per bar ( 1 per 1 coin)
Hard metals 500xp per bar ( 5 per 1 coin)
Silver 1000xp per bar ( 10 per 1 coin)
Gold 2000xp per bar ( 20 per 1 coin)
These are arbitrary numbers and would need some balancing over time, the obvious issue is Botting experience but this can be solved by removing lower currency from using this setting this system to silver/gold only.
The players would have the choice to melt the metal, receive the bars. Absorb the XP and destroy the coins or keep the coins.
This creates a good sink of resources, backs currency and will stabilise currencies demand.
This will tie into a future suggestion on realms, villages and Buffs.