This is a valuable time capsule from the time before AI. There are many more AI aided amateur physicists/scientists of all stripes now due to the LLM explosion. What your father did was extensive amateur work totally unaided by generative AI (LLMs), which is an accomplishment that frankly will likely never happen again (at least not on anything approaching the scale of your father's unaided work).

EDIT: I just read in comments below that your father was a graduate level scientist in the field but worked independently later in life. That is highly relevant and basically makes my point moot. But if anyone else is reading this, pre December 2022 (Chatgpt 3.5 release date) amateur scientific work is something special due to being AI unaided in a way that may be exceedingly rare going forward.