Currency, or money, is always something considered rather important. There are two currencies of use in the comic , credits and coins.
Used outside of the Magience, on Earth. 1000c, or credits, is equivalent to 1$ USD in 2012. Credits don't actually have a corporeal existence like dollars and change, they're received and spent digitally through the use of a virtual bank account attached to a person's identity from birth. People can use vouchers, little plastic cards, to transfer credits from one person to another. The account can be accessed through a device called an Access Scanner that scans an individual's retina and tongue print, confirming their identity. Only licensed businesses are authorized to have an Access Scanner.
Used inside the Magience world, there are three types of coins people use to make purchases: copper, silver, and gold, the standard three for fantasy worlds. They are grouped into 100s: 100 copper is equal to 1 silver, 100 silver is equal to 1 gold. If converted to 2012 USD, 1 silver would be 1$. Most things are priced in terms of coppers or silvers, since only the wealthy or adventurers/Sleepers have gold handy, the most notable exception being Legacy Items .
Large amounts of gold can be taken to the bank and exchanged for a voucher. In this way, people can carry a lot of money at once or hide it if they wish. Vouchers are bound to the owner and cannot be stolen like coins can, but they cannot be used to purchase anything and must be redeemed at a bank.
Often different countries or regions will have different names for their coins, some even bearing different embossing designs on their surfaces. However, they still accept coins from other countries since there are globally accepted standards for the minting of coins regarding weight, diameter, and purity of the metal so all the coins are roughly the same value.