Context : The Weimar Republic, the successor state to the German Empire, implemented a program designed to update their remaining supplies of Gewehr 98 rifles for the Reichswehr in the years following World War I. Rifles allowed into service with the early Weimar security forces were stamped with a ``1920'' marking on their receiver ring. 
Subject : Gewehr 98 
Relation : service entry
What year was Gewehr 98 made?