I found this information in this page .
http://www.collectiblefirearms.com/RiflesMauser.htmlTthe difference with my rifle is that mine is a three digit SN and the scope is not original,
"very scarce German Danzig factory Mauser M.1898 sporting rifle in 7.92 x 57 mm caliber. Manufactured by Gewehrfabrik Danzig shortly after the end of the Great War, as indicated by markings on the receiver rail and by the proof markings on the receiver ring. Sporting rifles of this pattern were manufactured in very limited numbers by the Danzig factory in 1918/1919. The lack of the military orders forced the Danzig factory to manufacture guns for the civilian market. Shortly after, the Danzig arsenal ceased to exist. Based on the Versailles Treaty all the machines were moved to Warsaw, Poland in 1920, in order to create the rifle factory there. The Danzig sporters utilized strong Kar.98AZ action with small ring receivers. Since Danzig sporters were arsenal made, they bear no commercial proofs, but Imperial German stamp, "Prussian Eagle" (stamped on the left side of the receiver ring, on the barrel under the wood, as well as on the bolt). Today, Danzig sporters are very difficult to find on the collector market, as very few were manufactured originally, and even less survived to these days. The receiver has German style scope mounts.The scope itself was manufactured by Dr. Walter Gerard in Charlottenburg, Germany, and is accordingly marked. Stepped, round barrel. Double set trigger. Military style stripper clip guides are machined into the back of the receiver. Internal box Mauser-style magazine. Fixed, European sporting style front sights. Two position, express style rear sights. Steel trigger guard. Walnut, sporting style half-stock with cheek-piece and semi- pistol grip. Beautiful diamond checkering at the wrist of the buttstock. Schnable forend. Mauser style safety lever is located on the back of the bolt. Turned down bolt handle. Steel buttplate. Two sporting style sling swivels. Manufactured with no provision for the cleaning rod. The four digit serial number indicates a limited production. All matching serial numbers (the matching serial numbers are stamped on the receiver, barrel, bolt, scope and scope mounts; all the remaining parts of the rifle do not display any numbers). The lower part of the buttstock displays a small crest of the city of Danzig, "Crown over two Crosses in the Shield".