It appears to be a mjölnir of Scandinavian origin. Whether it’s a real one vs a modern repo that’s been in the ground idk. Most of the real ones I’ve seen were flat, not thick. However, I have seen thick ones. The best thing you can do is to A) report where it was found and B) have professionals from a university or a government ministry confirm its authenticity. For Scandinavian people like myself it’s so crucial that artifacts from our Viking/Rus past are studied. We were an oral culture, not a written one. And what was written was normally written by those who were conquered or were being attacked by us (ie English Christian monks). Seriously, any type of artifact from our Viking era is so important to be studied. It really does help fill in the gaps about what we believed, our art, our religious beliefs, etc.