I have a bring back BYF 44 that is as bright at that rifle. I've had it since 1969 and I know that the fellow I bought it from for $20 didn't refinish it.
Mine has the same issue I can see on the OPs rifle and that's the Russian Capture, refinished extractor with the reddish hue.
Mine is that way because the original extractor broke and needed to be replaced. I have an un numbered extractor that has the same Nitre Blue the German's used to darken their steel to replace it with but just haven't gotten around to it.
The finishes on some of the Kar98 rifles was as good as and in many cases better than a lot of sporting rifles.
Let me give you some shining examples, 1908 Brazilian contract and the 1929 Persian contract rifles.
If you look at the stamps on the rifle, none of them have been rounded from polishing. All of the stamps are sharp and clear.
I can't see the serial numbers on the bolt or the trigger guard so I can't tell if it's a rework.
By the way, I also have a Russian Capture that has a finish that would rival the finish on that rifle. The Russians didn't bother to reblue barrels actions that didn't require it.
Again, the only issue I can see on that rifle, is the extractor. That isn't a big deal either.
another thing, those stocks got pretty smooth from being carried a lot. Dust, dirt, and other grit being rubbed into the finish while it was being carried with both gloved and bare hands, make a very fine sand paper. Add the grime and oils from hands and other things, and the stock gets exactly the patina you see in the pics.
I've personally, handled thousands of such rifles that were piled 150 rifles to a pallet, stacked across each other and steel banded to stop them form moving around with finishes as good or better than that rifle.
In the late sixties, I saw hundreds of K98s still being issued and again in the mid seventies.
The ones that were taken care of by the soldiers/police that carried them, had stocks that were very smooth from constant use and were being regularly oiled, which gave them a darker patina.
OP, that rifle does look to be a Russian Capture or maybe some other Soviet sattelite capture. Not only the Russians refurbed them after the war. To my knowledge, only the Russians managed to get the iron on some parts to turn that reddish hue.
Either the extractor was replaced because the original broke (not uncommon) or the piece is one of the nicer Russian captures.