This is a copy of a piece which was recovered from a viking ship in a find. The find dated about 900 AD. It was found as part of a hoard near Romesdal, Bornholm Island, Denmark and is on display along with other items in the hoard at the Roskilde Viking Ship Museum in Roskilde, Denmark.
As Christianity started converting people and those people took up the cross, the heathen Viking adopted the hammer, the tool the popular God Thor used to strike lightning. Thor named it "Mjølner." It was used as an ornament during the last century before Christianity was generally accepted in Scandinavia.
This piece is approximately 1 1/4" high and 1 1/2" wide.