I actually got a couple of hits on familysearch for Arron M Allen, but don't know enough to draw any conclusions. Both link to images, one notation for NJ F 3rd, so maybe a unit?

"United States Veterans Administration Pension Payment Cards, 1907-1933," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/K6WB-L3L : accessed 03 Sep 2013), Aaron M Allen, 1907-1933.

"United States General Index to Pension Files, 1861-1934," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/KDPP-DYR : accessed 03 Sep 2013), Aaron M Allen, 1862.

Val