OK, basically, you want a thin oil, not a thick one. I have no idea what's on the market in Norway for lightweight oils. I mentioned 3-in-1 because it's the common all-purpose household oil for sale here; it's really too thick for pocket knives. (Although years ago, of course, I used it all the time on my Boy Scout knife.) Talk to somebody knowledgeable at a hardware store and mention that you need a thin oil for a folding pocket knife. Bring it along to show.
Because the blades and tools on your knife are stainless steel, rust won't be a problem. Aside from keeping the edges sharp a major topic in itself maintenance will be mostly keeping dirt, grit, dust, pocket lint, and gunk out of the moving joints, and lubricating them as needed maybe once a week, unless you are using it a lot.
Keep a used toothbrush handy for cleaning out the tang areas. The bristles will get oily, but that's not a problem.
Yup, I wil try to find some suitable oil for the purpose.
Thanks

Whenever you consider giving a child a knife that has sentimental value, you have to consider how you would feel if your child lost the knife. I'm not suggesting that your son is irresponsible, but sometimes children lose things (sometimes grownups do too).
If the knife has sentimental value to you, then I would suggest keeping it and buying your son a new one of his own. I know they aren't free, but if you were willing to buy new scales and pay the shipping, you could apply that money to a new knife instead.
Then you can have your knife, and your son can have his knife.
Receiving a knife from ones father is great. But it's no less great, and no less a cherished treasure, if the knife is brand-new.
The oil sold for sewing machines works great for folders but might not be ok for food prep. I like the idea of keeping "this is mine!" inscription from your youth.
Yeah, perhaps I will buy him a new one. And the he can scratch hsi name into that instead

I would help him scratch his name near yours on that side.
He might just get his own knife, and he can have mine later in life, if he wants

^^I reckon that would work.
Alternatively if you do want to sand you should be able to get that out it doesn't look too deep in the photo. I agree though that a good polish with something like Flitz would do wonders.
Failin g that have you considered making a set of wooden scales for it? I've done that to SAK's twice so far and it really lend something to the knife, timber being such a warm material.
Nope, but I read somewhere that making scales for these types on knifes are a bit challenging? more so than ordinary scales that can bolt\screw on?