The economy in King's Gate seems to have its diverisity, with each kingdom or empire having their own economy to use for commerce and trading alike. The concept of silver coins and golden coins exists, but is more officialized through banks and minted coins by the respective kingdoms. Below are a set of economic systems that exist within the grounds of Mythage.
The Aetherin system follows closely the concept of bronze, silver, and gold coins, but retians an additional coin, copper, it being the lowest denomination and used for low-end transactions. Here you will find the link to the aetherin guide.
Karn = Copper | Brassil = Bronze | Argent = Silver | Solari = Gold