brunetp, it may not be a Russian capture. Most of the countries the Axis troops, occupied during WWII, had K98s and all sorts of other firearms, laying around all over the place. Warehouses, battlefields, town squares, hidden in barns etc. Same goes for Allied weapons and kit.
The Russians, weren't the only ones that hated the waffenampts or swastikas. That rifle, could have had the marks stamped out anywhere.
What the fellows are really trying to tell you, is that the rifle has been modified, as well as re assembled, by a captor. You won't be able to change that. I'm surprised, that only the receiver isn't matched to the other parts. To have a K98, with a bolt that is matching all to itself and the rest of the rifle, having numbers that match the receiver, isn't unusual. It happened a lot. Many Axis troops, as well as their captors, pulled the bolts and either threw them away or put them in separate piles. Their chances of being reunited again, became impossible.
Your rifle, is a legitimate collector, as is. The fake stamps at Numrich, are very easy to spot. I understand why you want to make the waffenampts clearer but it would detract from the legitimate history of the rifle and actually devalue it.
Another sad fact, there are a lot of put together from parts rifles out there now. People, are scrounging up old parts bins, or buying the parts to assemble complete rifles. These "bitser" rifles, are pretty easy to spot. It they're done properly, they shoot well and you don't have to devalue a fine collectable specimen, taking it to the range.
Leave it alone. Live with it. 20 years from now, it will have tripled in value and you won't be sorry. The fact that is is ex Nazi, is already obvious by the peened out waffenampts.