Context : The PTRD-41 (Shortened from Russian, ProtivoTankovoye Ruzhyo Degtyaryova;Противотанковое однозарядное ружьё системы Дегтярёва образца 1941 года;``Degtyaryov Anti-Tank Rifle'') was an anti-tank rifle produced and used from early 1941 by the Soviet Red Army during World War II. It was a single-shot weapon which fired a 14.5×114mm round. 
Question : What was the year that PTRD entered service?
1941