Appears to be a DT, the tank mounted version of the DP or DPM light machine guns, based on the mag, and if I'm counting the rd number markings correctly. DPs use a 49 round drum mag, while the mounted DT versions use a 60 rd drum. Can't tell which one you've got here by the pics. Tank model DTs do not have a quick change barrel, while most of the rest of the DP family does.