I am the currency of a nation known for its fjords, Vikings, and a history of seafaring exploration. My value is closely tied to the price of crude oil, and I am not part of the Eurozone despite my country's proximity to it. Historically, I was pegged to the price of gold but not anymore. My central bank is known for its independence and its role in managing a large sovereign wealth fund. What currency am I?

1. My country's capital is also its largest city and an important international port.
2. My name can be seen on a type of banknote that has a prominent image of a famous playwright and theatre on it.
3. My ISO 4217 code starts with the letter 'N'.
4. I'm sometimes informally referred to as 'the krone'.