Context : The DShK 1938 (ДШК, for Дегтярёва-Шпагина Крупнокалиберный, Degtyaryova-Shpagina Krupnokaliberny, 'Degtyaryov-Shpagin Large-Calibre') is a Soviet heavy machine gun firing the 12.7×108mm cartridge. 
Question : In what year did DShK enter service?
1938