Congratulations! A really nice example of an early Suhl Mauser. Obviously this rifle was built by or for Ed.Kettner on an original Mauser, Oberndorf commercial action. Pre-WW1 Mauser patents were still valid, so everyone wanting to build a M98 action rifle had to buy an action from the Mauser factory first. Up to 1914, Mauser sold about 70% of their commercial production as “actions only” or barreled actions. These actions are easily dated by the Mauser commercial serial number and the help of Jon Speed’s book. On the actions sold by Mauser to other gunmakers you find the serial number under the receiver ring , behind the recoil lug, and on the rear wall of the magazine. As the Suhl gunmakers did not care about “matching Mauser serial numbers”, they quite often mixed up upper and lower metal, especially as they often converted the military floorplate to lever opening or detachable like on your rifle. The opening lever was a Suhl improvement, only later offered by the Mauser factory too.
Eduard Kettner, Köln, had a branch in Suhl from 1910 to 1925. The proofmarks under the barrel may also date the rifle. If a gauge number like 172,28 or 156,14 is there, it was proofed 1910 to 1912, if the bore Diameter is given as 7,8mm it was completed 1912 or later.