Remains of bone and wood, found in a tomb next to the stone and dated by radiocarbon analysis, suggest the runes were carved into the stone between AD 1 and 250, the museum says. The discovery is "a dream come true for runologists" who study runic alphabets, according to the museum.

Rune stones are inscribed stones that were usually placed on graves - especially during the Viking Age. The inscription "Idiberug" can be read on the stone of Tyrifjorden, which was probably intended to pay tribute to the deceased buried in the tomb.

So far, stones found in Norway and Sweden from the years 300 to 400 AD were considered the oldest rune stones, as the expert Kristel Zilmer told the Norwegian news agency NTB. The find at Tyrifjorden is therefore a "unique discovery". The stone can be seen from January 21 to February 26 at the Museum of Cultural History in Oslo.