Fresh from the ground, after having been buried for hundreds of years.
The rather well written runes, done by someone who knew what they were writing.
The marks suggestive of crosses on the reverse.
Translation experts believe that the runes say something like "Come uninjured from the curses..." or something similar.
In the Middle Ages, folk were much more superstitious, and when sick believed that they may have been cursed.
There is a well known incident from the old Egil Skallagrimsson saga from Iceland, where Egil cures a sick girl, Helga, who found that she couldn't sleep and who felt her soul, through witchcraft, had been injured. Looking in her bed, he discovered a bone with menacing runes. After he removed these runes, Egil wrote his own runes of healing, and had Helga put them under her pillow, after which she immediately recovered.
This object that Mr. Lindberg has unearthed is thought to be a similar "curing" stone, used in the same way as Egil did.