In EverQuest, the currency system (Platinum, Gold, Silver, Copper — PP / GP / SP / CP) is a purely abstract numerical representation.
Players/GMs often invent their own flavor: "Norathian Standard Minted Platinum," "Faydark Gold," "Kunzar Tribal Copper." But this is headcanon, not coded reality. The Banker NPCs simply increment/decrement numbers.
So: They are made of data. Pure math. No ore, no mint, no metallurgy.