The only break from the decimal money system, a minim is a half-sized copper coin, worth exactly that much. To differentiate them from the usual coins, they are half-sized by virtue of being minted in half-moon shape, and not a full circle as is common. It is used by the very poor who purchase small amounts of items, as they are often unable to afford large purchases at a time.
Unlike copper, silver, and gold coins, there are often only very few minims in circulation at any time, their use carrying social stigma of the poor and perennially tightfisted.
They were put in use during the early years of the Royalist Era by one of the first Kings. The idea being that smaller coins would help the lower levels of the economy move more smoothly, and quickly- the poorest not having to wait for a full copper to purchase something.