interesting. wonder whyWelcome to the forum. My Böker Barlow has a similar mark on the tang. I never noticed it before I read this thread and looked for it.
So boker support got back to me and said it looks like they forgot to polish the tang. They said if i sent it back for a replacement, they would give me the credit for the shipping and handling i would pay. I'm just going to keep it though. I'm satisfied with a mystery solved.