@vagabond
The "Custom range.." for the ordinary WebSearch relates to when things was publish to WWW.

I just did two ordinary web searches for first [apple] and then [cat],
and then I set the "Custom range.." to the interval [1/1/1800 ; 1/1/1920]
I did not find any results at all, and I would have been slightly surprised if I did, since the Internet did then not exist.

As far as I can tell, then ... I think you're out of luck with Google.
Your local librarian or historian is probably a good person to ask for advice on what good search/research tools are in existence.

I remember that Google once had a project (I can't remember the name) with getting historical documents scanned, onlined & indexed - but that project was axed "long" ago. So - Sorry, but I think you need to drop the idea that Google will help you and other historians.