There have been a few vises and other notable equipment (Canton crane, Delta DP, workbenches, etc) posted sporadically down here on the Vintage board sporting DPC tags and several vises on the Mega Vise thread on the General board. There are no known records on Internet Archive or Google Books to look up that number on the tag and it's almost impossible to know where it came from without other information.
Just to clarify, the DPC was not a military organization, per se. It was a quasi-federal government, quasi-corporate entity that was part of FDR's Office of Emergency Management, prewar, and then interrelated with the War Production Board after we declared war. It was established explicitly to equip the war production industry here at home. DPC expanded existing mfg facilities, converted civilian mfg facilities into military production facilities, built new plants, and outfitted them all with equipment, from vises to machinery. They bought your vise on contract from Columbian and then put it, likely with many others, in a mfg plant somewhere to assist some company make materiel for WWII. Your vise was never issued to one of the technical services (Army, Army Air Corps, Navy, etc). It was in a civilian plant turning out something for shells, planes, vehicles, etc. That's not to diminish or dismiss its valued service or coolness factor. Just clarifying.