Since Spandau (near Berlin) was a Prussian Arsenal, it is almost certainly one of several variations of the German Army issue rifle based on the Mauser 1898 action. It is possible that it was a war souvenir from WWI or even WWII, because many older rifles were rebuilt and reissued in the later era.
If the rifle is unaltered, it is in what we call 8mm Mauser, or 8x57 (the German army called it the 7.9). However, that date is right at the point of conversion from the old 8mm ammunition to that with a new and larger bullet. If the chamber is not marked with an "S" or in doubt, have a gunsmith slug the bore before firing.
Jim
