Precise weights of hacksilver are quite common in archaeological digs and treasure hoards, and the Norse used touchstones to verify purity of gold and silver. They were serious about trade. If memory serves, viking comes from their term for going raiding, but they also explored the rivers and seas around Europe. The Normans descended from vikings. The Vernagian Guard in Byzantium were usually vikings.

You probably know all that already, of course.

The vikings settled not only Iceland, Greenland, and Nova Scotia, according to some dedicated true believers, they made it all the way to Minnesota. I have seen the stone, but I can neither verify nor disprove its authenticity myself. It does, however, come from an era with a lot of fraudulent finds and hoaxes.

Edited for autocorrect typos