The article remarks on how it would have been a very heavy sword. This suggests to me it was a ceremonial sword, as a too-heavy fighting sword just means you're going to die. Or maybe the missing blade is just stuck in a stone somewhere.
But, since the blade is missing, we don't know how big it actually was. It's funny to me that they have just a handle but they keep calling it a "sword".
By the way, didn't Beowulf bring back just a handle after the fight with Grendel's mother? Maybe he started a fashion. :-)
But, is it magic?
It may have been a scimitar lobbed by some moistened bint.