1. Which period? Pre1821 there is no reliable history. Between 1821 and 1874 it was that of Sierra Leone. After that it's a little murky, they used goods for services and gold dust/rocks by weight periquins/ackies etc along with European currency for a while - A few dutch silver coins were there, but not much. A bit more dutch silver after 1870
2. European coinage, by proclamation. For the most part.