It is obviously a German military large ring 98 Mauser. It has a Nazi eagle Waffenamt stamp on the root of the bolt handle, so the bolt appears to be WW2 vintage, but the lack of Waffenamt stamps elsewhere makes me wonder if the bolt isn't original to this rifle and if the bolt is newer than the rest of the parts with matching numbers.
German military Mausers were chambered in 8x57, so if this is your next 7x57 project, I assume that it either has been rebarreled or you are going to rebarrel it. It looks kind of rough, maybe stored under poor conditions after it was captured, I don't recall seeing another 98 with a divot like the one in the receiver bridge.
I believe you are correct about the bolt not being original as the rifle has crown over N proof mark.
Shew me thy ways, O LORD: teach me thy paths. "there are few better cartridges on Earth than the 7 x 57mm Mauser" "the .30 Springfield is light, accurate, penetrating, and has surprising stopping power"
