That is what is left of a Mauser Mdl. 1888 Comisson Rifle. The standard of the German Army before the Mdl. 1898. These are "S" Bore .323 8MM Caliber. The later "J' Bore .318 8MM was used in Mdl. 1898 of WWII.
The Mdl. 88 Mauser had the split bridge Mannlicher type action. The Mdl.98 Mauser had the solid bridge action. These are not strong actions and you must use the correct ammo.