Bolt has been renumbered. Bolt body, bolt shroud, and safety at the least. That numbering does not look like any arsenal renumber job I've ever seen, although I'm not the expert on those. I'm going to say that was done later on by someone else, but I'll defer to anyone more knowledgeable. I have no idea what's going on with the numbers(?) and proof mark(?) on the under-side of the bolt handle, although I can say they're not original. Was the gun privately owned in Europe at any point? I'm half wondering if it had to be re-proofed when the bolt was replaced.
Stock is a replacement, but was at least numbered to match. That looks consistent with it an arsenal replacement, although again I'll defer to the people here who really know arsenal overhauls.
Small parts on the bolt (cocking piece, firing pin) don't match.
I don't know who put that SN on the inside of the floorplate, but it wasn't the Germans. It should be on the outside and centered vertically for them. I don't know if this was a post-war user (e.g. another military) or just an idiot who didn't know better.
I'm not a fan of the trigger guard. Numbers don't look quite right to me and it doesn't look like it has the inspection marks a pre-war Borsigwalde should have. That said the numbers don't look quite as "Harbor freight punch set" as the bolt numbers so I'll recognize the possibility it could be an armorer replacement, perhaps when the stock was done. Again, I'll defer to the people here who really know armorer/depot overhauled guns.
Barrel bands should be numbered to match the gun. They're not. On the plus side at least they're not badly renumbered. Again, perhaps a depot replacement? Don't know, I won't weigh in on that. But the sling arrangement isn't right and I doubt that would have been done as part of WW2 era depot work.
How much are you into this gun? If it was sold to you as all matching I'd try and get my money back if you can. If you bought it for shooter prices, though, you might be doing fine.
Here's what a prewar S/243 should look like. A year earlier but still representative re: things like how the bolt numbering should look from that factory.
New set of pics of one of my favorites. A bit salty for sure. Plus, someone in it's history didn't quite understand the lock screw concept:
www.k98kforum.com