Context : The lMG 08 and lMG 08/15 guns would always be used on fixed-wing aircraft, as fixed forward-aimed synchronized firing ordnance initially in single mounts for Germany's 1915-16 era Fokker Eindecker and Halberstadt D.II ``scout'' single-seat fighters, and by 1916 in dual mounts, first appearing on the mass-produced examples of Robert Thelen's Albatros D.I and D.II fighters in late 1916, and singly on German ``C-class'' armed two-seat observation aircraft for synchronized forward-firing armament. 
Subject : MG 08 
Relation : service entry
In which year was the service entry date for MG 08?