Of Course, the Adjutant General's name caught my attention and I had to research H.P. McCain. Turns out Henry Pinckney McCain was a distant uncle of John McCain (U. S. Senator, Arizona). H.P. McCain set up the World War I draft and became known as the father of Selective Service.
Inside the front cover is the brief inscription: J.C. Benko, 631 Aero Sqdn.
Of Mr. Benko, I can find nothing. I could almost say the same for his phantom-like 631st Aero Squadron. A Wikipedia page produced a clue about the squadron's origins:
(Note war declared 6-April-1917)So the 631st was an Aero Supply Squadron. And Mr. Benko must have gotten hold of this book in 1918 after the numbering scheme went into effect.
In January 1918 a new numbering scheme for aero squadrons was set up. Numbers 1-399 would be for Aero Service Squadrons (AS). 400-599 Aero Construction Squadrons (ACS), 600-799 Aero Supply Squadrons and 800-1099 Aero Repair Squadrons.
A note to World War I historians who might be searching for the 631st: I found the following information about this squadron on a genealogy forum:
The 631st was redesignated from the 46th Aero Squadron in Feb 1918. It served at Garden City NY until demobilization in 1919. There was another 46th Aero Squadron that maintained that designation in Texas. The 631st was an Aero Supply squadron. There was a lot of reorganization and redesignation of units as the aero corps expanded which is why there are two units designated the 46th.A follow-up post on this forum adds anecdotal information about a relative having served in the 631st and where they served in France when deployed there during the war.