Aeldreth’s economic and currency system was created by the Triumvirate, the triple gods of trade and craft, Nuatha, Gofannon and Llew. It is a global system, with all nations and realms using the same currency.
The currency consists of three denominations of coins and high denomination bank notes. The coins are named for what they are made from: coppers, silvers, and golds. The metals have no intrinsic value themselves. The basis of their value is the overall trends of the global economy as calculated almost constantly by the gods and their clergy.
The base coin is the copper. A silver is worth 100 coppers, and a gold is worth 100 silvers.
Paper bank notes are called celestins. They are issued by banks in denominations of 10,000 gold and higher.
New coins are minted and celestins are printed by the High Temples of the Triumvirate in each of the governed realms (excluding Caillun). The currency is then sent to the High Court, which distributes it to the nations for circulation via banks. New coins bear the emblem of the Triumvirate on one side and are blank on the other, which is stamped with the emblem of the High Throne and the emblems of the nation they go to next before circulation. That is how international and inter-realm trade is roughly tracked.
Likewise, celestins are printed on one side by the temples, and on the other side, they are printed by the Thrones and nations. Their values are written in by the banks that first issue them, and then they are rather like bearer bonds, carrying their face value for whoever happens to hold them. For security, celestins are enchanted by the temples to recite their own transaction histories when the right spell is spoken.
This system of cash is used for everything, but barter is still also widespread, especially in very rural areas. Quite large transactions can be conducted by trade-in-kind. Even taxes may be paid in kind under some circumstances, and rural tax collectors travel about on their annual circuits like caravans loaded down with livestock, grains, and other goods all valued at audit as equivalent to the taxes owed. It’s up to the local governments to convert goods into money.