what metal is it made of?
replies(1):
> if it was an outlier like meteoric iron (a) it would look like it (corrosion)
It is corroded. That's why it's green.
Which, yes, means it's bronze, but note that it's being described as an "iron age dagger" and they think it was manufactured in southern Europe and traded to the north. Iron wouldn't be surprising.
https://www.britannica.com/place/Hallstatt-archaeological-si...