Interesting board. Don’t know what he told you about his service, but I can tell you what I see there…
I see your Grandfather was a Warrant Officer — an expert with two weapons and a Marksman with two others. I also see a Silver Star, a Legion of Merit, a Bronze Star, a Meritorious Service Award, an Air Medal, several Army Commendation Awards, at least one Army Achievement Medal, and several others. I see he served in Vietnam, also receiving the Vietnam Civic Action Medal...bet that's an interesting story!
He was a Paratrooper and appears to have been qualified as an Aviator or aviation crew member.
He was assigned to the US Army’s 2nd Field Force (find out more about them
Here). It seems he was also assigned to the Criminal Investigation Command (“CID”) . . . a group we used to refer to as “Super Spooks” when I was merely a “Spook” with the Army Security Agency in Berlin working with the NSA.
All in all, quite an interesting guy. Wish I’d had a chance to sit and chat with him.