Some nice pieces in there, I'm rather partial to pre ww2 aaf collar devices and love the 5th bombardment group DUI, missing one myself. Do I see some unusual bullion parachute wings in the first image? 

As EE87 posted earlier, here is the unauthorized Combat Mortarman Badge:     I don’t yet have the unauthorized Combat Machinegunner Badge that this company, Goons Up, made.

They look good, but I sometimes have trouble delineating WW1 from post-war manufactured hat cords.

This photo looks to have some of the same people in it. Fort Mojave did use Mojave's as scouts.

I didn't know that about the hat disks, so its complete fantasy when coloectors claim its correct for ww1. But you are right so many collectors do that with campaign hats. Regarding the cord would this be correct for medical department? I don't think its engineer it doesn't appear to be the same color. Unless the red faded over time.

Living in Montgomery in enjoyed the post card.   Great research and thanks for posting the hat.

Greetings,   Avirex (1998 contract) and Cockpit (2007 contract) models had two interior pockets and a pen pocket.  Keep in mind when pen-pocket is mentioned, its in one of the two interior wallet pockets, not on the sleeve.  These models are also found with side entry pockets.  Weird side note:  The Avirex and Cockpit models are identical to a reproduction A-2 made by Banana Republic in the 80's   Best,   PEter

Sure they would. I don't think the design details changed until after the war. I also don't think early or late WW1 service hats were much different if at all. Plus, just because an item changed somehow doesn't generally mean the older stock would not be sold or issued until exhausted.

Yeah there's definitely evidence to support everything so far. That also explains the hat, he probably bought the hat in Montgomery when he was in Alabama for training. But then the question comes would early campaign hats still be available for purchase in 1917/1918? It looks like he enlisted in August 15 1917 if thats correct?

Could be both, I believe.