Aether Coins
Aether Coins are made of fragments of Shellite shells, and in the modern era function both as the primary currency, and source of magic in the world. They can absorb and retain small amounts of Aether, the mystical energy that powers all sorts of devices, weapons, and machines in the current age. As such, these coins are extremely valuable in society. 1 charged Aether Coins is worth 10 depleted ones. Power and magic systems use a unified measurement scaled related to Aether coins, using the Shell Equivalent Units (SEU) measurement scale. The amount of charge that 1 Aether coin can hold is equal to 1 SEU. Various devices and machines will consume SEUs at certain rates, like 3 SEU/hour, 1 SEU/day, etc. Also, with the exception of Aetherites, in order to cast "spells", casters must utilize SEUs to perform their abilities (see Magic and You).