Ponies on the Isle of Yore and its vicinity use a variety of currencies and media of exchange.
exchange rates table here
Bits
Bits are a common form of currency taking their name and physical appearance from an ancient Equestrian currency. Many of the original coins are still around, due to long-lasting anti-wear enchantments. Although originally fiat currencies, their distinctive enchantments are very difficult to duplicate, and there is an effectively limited supply of old bits. The city of Docktown has recreated an approximation of these enchantments, and New Equestria claims to have retained knowledge of the numismatic magic from Golden Age Equestria. Both of those entities mint modern bits.
Docktown Bits
New Equestrian Bits
Old Bits
These coins represent bits minted by pre-Catastrophic civilizations. Old Bits have steadily deflated over time as anti-wear enchantments fade, they are lost or hoarded, and so on.
Bucks
Precious Metals