The Litia

The Litia (pronounced Li-shi-a) is the most common currency of the world. It’s a tiny magical gem in a small magical metal disc. What makes it useful as a currency is that it has uses outside of being a currency. Magic is capable of being stored in the gem, that can be used by anyone with the ability to caste any kind of spell or ritual. It has four defined states simply by the way the gem is cut: New (empty), First Quarter, Last Quarter, Full. The gem fills like the phases of the moon, so any layperson can tell exactly how much magical energy is stored in there. Two partially filled Litia can be mashed together to make the sum of the two up to a Full Litia, and similarly divided. This is the most common way of determining the authenticity of the coin, since counterfeits cannot merge with authentic ones.

D&D currency conversion:
Empty: 1 copper
First Quarter: 1 silver
Last Quarter: 1 electrum
Full: 1 gold