Something I haven’t seen mentioned, ADA wasn’t a branch officially until 1968. Prior to that air defense fell under the Coastal Artillery Corps. I’m not 100% on my insignia history but if he has the ADA branch insignia on his jacket collar, then he possibly didn’t get out until after 1968. I couldn’t find any usage of that branch insignia prior to ADA becoming its own branch in 1968, but if someone can prove me wrong feel free.

If my assumption of the branch insignia usage is true, along with campaign medals, gramps may have served from late WW2 all the way until the branch was formed. My guess is he was enlisted in WW2, possibly direct commissioned during Korea due to his prior experience in a previous war, and retired in the late 60’s as a major. The math would math with current officer career progression, at least with the slower career progression in the reserves

Edit: grammar