If you can find any old photographs of him in which his shoulder patches are clearly visible, remember that the armored division patches were very similar (triangular in shape) but listed the numeric designation at the apex (1-20). It is also possible that he was in an independent tank battalion or similar tank destroyer battalion which was assigned directly to division through army group levels. Many folks referred to them as tanks and can't tell the different between the common Sherman tanks and the various forms of tank destroyers. The letters written home, heraldic crest, or uniforms (Photographs ) will solve this the most quickly. If you find any references to numeric units, please post them. Tank battalions, whether organic to divisions or independent were in numbers typically between 1-812 (example 99th Tank Battalion) but the tank destroyers were seen in series from 601-899 (example 811th TD Battalion). Also, many units can be eliminated from your search solely because the army was, at that time still segregated and units that were African-American are identified as such.Good Luck! Rick