The Hindsgavl Dagger is an exquisite Neolithic flint tool, found on the Danish island of Fænø. It was made around 1700 BC, when metal knives were already starting to appear in Europe.
Pieces like this, known as fishtail daggers, were still made from flint, but were specifically modelled on the metal versions spreading across the continent. They show the extreme lengths, and incredible skill, that flint workers deployed in order to compete with the new-fangled metalworking technology that would eventually make their craft redundant.
You can read more about the Hindsgavl dagger in the archives of the National Museum of Denmark.