His WW I draft registration describes him as short of medium build, with blue eyes and light brown hair.
Sources
"United States Census, 1900," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/MSLC-LYG : accessed 27 Jul 2014), Glen Harter in household of William B Harter, Parrish Township Parrish village, Oswego, New York, United States; citing sheet 3B, family 86, NARA microfilm publication T623, FHL microfilm 1241144.
"United States World War I Draft Registration Cards, 1917-1918," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:KXBW-H4T : accessed 16 January 2016), Glenn Gilbert Harter, 1917-1918; citing Oswego County no 3, New York, United States, NARA microfilm publication M1509 (Washington D.C.: National Archives and Records Administration, n.d.); FHL microfilm 1,818,708.
"New York, County Marriages, 1908-1935," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/XVPC-WDX : accessed 27 Jul 2014), William B. Harter in entry for Glenn Gilbert Harter and Grace Robertson Mosher, 20 Aug 1919; citing item 436, , New York, United States; FHL microfilm 872943.