Known. A boy of six found a sword in a field.
The field is at Brandbu, in Gran, Innlandet, Norway. The sword is believed to be about 1,300 years old. It is sharp on only one side. Swords of that kind belong to the late Merovingian period, about 550 to 800 AD, or to the start of the Viking Age.
The page is not sure which of those two times this sword belongs to.
https://www.ancient-origins.net/news-history-archaeology/merovingian-viking-sword-00102772