There is a research thread here that I maintain, but we need the date(s) on this rifle to include it. I assume it is an 1887 considering the unit marking falls into rifles from 1887 (typically unit markings correlate to rifles of the same maker-date and ranges, this is generally true of Kar.98a also, and probably G98's, though statistically we can't be overly confident because there is not enough data/rifles with original stocks amongst pre-war G98's to form consistent patterns).
Before I add it I would like to confirm the date of this rifle and that the buttplate shares the same serial.