The longer, darker marks are tooling marks.
The shorter, cross ways marks are metal galling.
Someone probably got a round under the bolt and jammed it up, tried jamming the bolt closed.
Sometimes mag lips dig into rounds & jam things up, your first reaction is to hammer the bolt handle with your hand, which will result in galling.
If the floor plate got past the stops at some point in it's life, the bolt can do that very thing to the floor plate.
Someone that FULLY strokes the bolt probably won't run I to these issues.
If you brought it to me, I would probably see how deep the marks are, if they can be removed that's the route I'd go. If not, I'd smooth the feeder plate and install a cosmetic cap on the feeder.
It's ZERO functional issue unless rounds jam and don't feed smoothly.
When EVERYONE trained on a bolt rifle, they were taught to FULLY pull the bolt back.
Many were trained to WACK the bolt rearwards, often the ejectors were fully reward and a WACK ensured positive ejection. (Old surplus military rifles in particular).
Now that so few train on a bolt rifle, a lot of short stroking happens causing issues just like this one.
I see the dents/galling in many rifles from the round ramming into it. This is short stroking dragging/wedging the round into the floor plate instead of pushing it correctly into the chamber.
If you are having no issues, you are fully cycling the bolt, Model 70s are pretty reliable, even the import versions, and with a full stroke they are reliable.