An interesting perspective is most of the suggested docs were written in the last couple years, at most. I think you'd benefit by finding retrocomputer people

An interesting perspective is most of the suggested docs were written in the last couple years, at most. I think you'd benefit by finding retrocomputer people and asking them about docs they've seen to find the best technical writing of the century. I don't have a short list of IBM Mainframe docs, but those are probably "the best documentation money could create" in the 50s-70s. Easily second best would be the DEC TOPS-10 Software Notebook Series which in my experience was a set of 20 binders and in one shelf it contained all you need to run a major 80s minicomputer operating system including apps. What 80s DEC documentation did VERY well, was every doc was planned out intelligently and in detail by actual users to make sense to a professional sysadmin on the job. Unlike "sales/marketing" driven docs, the software notebook series TRULY understood its audience of professional sysadmins. I also feel that 80s DEC documentation had the best intros in technical writing I've ever seen. Intros are underrated and the author(s) need to make a "contract" with their reader before throwing detail at them. Take for example, volume 6 or so of the dec-10 software notebook series which has the ALGOL programmers's reference guide with the best intro ever. "This is where you start" should be the most carefully designed and written chapter of the docs, not a filler chapter. In summary, don't skimp on outline and don't skimp on writing a real intro. Personally I like some of the Tandy/Radio Shack Z-80 manuals. Perhaps the extended basic manual for the model III, or the 6809 assembly book they resold are the pinnacle of late last century technical writing for a more general audience. Retrocomputing is a fun hobby that extends far beyond technical writing critique, obviously.