Currency

Currency (通貨, Tsūka) is any item accumulated and used to make purchases. While coins are a common medium of gold exchange that the inhabitants of the New World and the YGGDRASIL Players share, the value differs between the two.

New World Economy
In the New World, four metals are utilized as the monetary standard and valued in increasing value: Copper, Silver, Gold, and Platinum. In addition to that, there do exist financial institutions supported by the government. For example, the Imperial Bank located in the Baharuth Empire. Trusts in the form of metallic plates are used by the banks within the Empire, similar to that of a cheque. Trade between nations exists through numerous official and unofficial channels. Platinum in particular is used in international trade.

According to the Web Novel, all Trade of Currency, is marked with the symbol of the God of Business which is the wheel. And on the other side is the symbol of the merchant guild that issued the currency.

Exchange Rate
The exchange rate between the Re-Estize Kingdom and the Baharuth Empire is 1:1.

YGGDRASIL Economy
Unlike the inhabitants of the New World, players used only one type of metal as currency: Gold. In the past YGGDRASIL's coins went through two conversions in the past. Originally, the gold coins had the face of a man sealed upon them, before Valkyrie’s Downfall Event. It's current form has the profile of a woman, possibly a Valkyrie. YGGDRASIL gold had multiple uses, such as a medium of exchange for purchasing items, guild house maintenance, as a component in magic scroll and potion manufacture. After the Great Tomb of Nazarick's transfer to the New World, all the coins and valuables stored within the Treasury have been transformed into actual gold. Ainz has also discovered that compared to the gold coins that are used by the inhabitants, YGGDRASIL coins are worth at least twice as a standard gold coin in the New World, but due to the artwork on them probably five times more.

Trivia

 * It is unknown if New World coins other than gold can be used in Nazarick's NPC resurrection system. Thus Pandora's Actor has been charged in appraising all outside valuables in order to determine their value.
 * Ainz keeps an original coin of YGGDRASIL as a keepsake of his younger days of playing with his comrades together.