Well Z mentions mail ordering everything
Except one.
I’m just skimming through this thread and I’m sure it’s been thought if not mentioned directly but it’s possible that Z included that line on the back of reading these very articles about attempts to trace him via gun sales.
Nov 9th 1969
" 3 my killing tools have been bought en through the mail order out-fits before the ban went into efect. except one & it was bought out of the state."
For that alone these articles are interesting to perhaps give a reason/purpose to why he wrote that.
The newspaper mentions trying to trace/find weapons. Zodiac was just throwing them a bone, imo. He was a criminal. He could have purchased his guns from another criminal. It was good LE looked into it, but I have to think he was smarter than walking into the local gun shop.