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.
Last edited by 260Remguy; 01/13/18. Reason: corrected grammar/punctuation
