This 11th century bronze die worked with interlace would have been used to make the cheek guards of Viking helmets.
The design is known as Urnes style ornamentation and probably represents the world tree Yggdrasil with the monstrous serpent Nidhogg intertwining within its roots.
It was discovered in a field in Norfolk by a metal detectorist in January this year.
After posting an image on Facebook, it was identified as Viking in date and the recorded via the Portable Antiquities Scheme.
It fell a little short of its estimate of £16,000-24,000 but sold nonetheless at £15,000. The proceeds will be shared between the finder and the landowner.