But there is no way to know that for sure, short of physically examining the yearbook (ink composition, etc.). E.g., until proven otherwise, it could have been added by a 2017 Democrat operative, or even the yearbook owner, but in 2017, forty years after the fact.
The “D. A.” thing is odd, not his actual title and it’s possible that this was added later as well.
His actual title was Deputy DA, having been sworn in the previous 1 October.
Maybe his title inflation is significant, maybe not.
My signature changed significantly in the past 34 years, but the first initials of each name are pretty much the same in terms of the technique. I’ve never heard of a uearbook being released prior to Christmas. The whole purpose is to record events from the school year. They would have had to go to print in November, only 3 months into the school year.