Defenders of Aylanae
There are four precious coins accepted as standard Imperial currency: gold, silver, copper and a new coin called The Imperial.
The value of precious coinage is weight-based, often verified by an EVA.
The official trade value of a silver coin is 25 copper coins, and a gold coin is worth 10 silver coins.
Coins are weighted precisely and generally minted with the stamp of a great house. By imperial law, all coins must be made entirely of the valuable substance in question and must be a standardized weight per coin. There are non-standard coins still in circulation, which are only accepted at various banks, or by great Houses directly, who are then obligated to have them smelted into proper coins. Makoro especially has an abundance of non-standard coins of varying weights, and sometimes questionable compositions.
Creating counterfeit currency has steep penalties. All currency must be minted from real precious metals, and may not be the product of magic. Due to the accuracy of the EVA, this is rarely a problem.
The exchange rates of coins are determined by the Imperial Council, based on mining rates/minting of the various metals. Generally the exchange rates do not fluctuate unless there is a strong need to do so, and the beneficiary of a new gold mine generally doesn’t have to worry about gold getting devalued compared to silver or copper.