The information is correct. Sauer & Sohn was a German arms maker for both military and civilian guns. The rifle was German army issue; 1916 is the date of manufacture and was, of course, right in the middle of World War I. Probably the rifle is (or started out as) the standard Model 1898 rifle, but we would need more info and/or pictures to determine if it may be a less common variation. Also, if the rifle has been cut down or "sporterized", its restoration would be very difficult since almost no original parts, such as stocks, exist for rifles of that vintage.
Unless it was altered, the caliber is 8mm Mauser, also called 8x57JS or 7.9mm.
Jim