History of copper currency in Sweden
The Swedish Empire had the greatest and most numerous copper mines in Europe as it entered into its pre-eminence in the early 17th century as an emerging great power. Through poor fiscal policies and the First Treaty of Älvsborg, Sweden lost control of its reserves of precious metals, primarily silver, of which most had left to the burgeoning trade economy of Amsterdam.
Source: Wikipedia — History of copper currency in Sweden (CC BY-SA 4.0)