Going by the inconsistent spacing and angles on that 1984 PCB, I'd almost guarantee that it was routed using black tape on mylar film, not a CAD package to be seen. Trying to create large fills back then would require manual positioning of tape over all of the copper fill areas. Tools is a big part of the reason for the shift, it's easy now, and the results are generally much better.
I think that one was actually done in an early Japanese computerized CAD package. There's a lot of weird crap in that layout, but it's the sort that the old-school computer layout programs made, not the sort that humans did. Take a look around U111 pin 30, or south of R112, or, heck, any of the text. Whereas there's no sloppy-but-OK vias or wobbly text or anything like that.
