Research Source Guide

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I thought I'd put this list together of the places I use to research these old tools, just in case anyone wants to conduct similar research. 

Google Books - Excellent source for old magazine / publication articles, books, advertisements, etc.  (HINT: USE the search tools at the top of the page when searching for specific date ranges, etc.)

Worldcat - Searches hundreds, if not thousands of library archives for online editions, editions in their holdings, etc.  You can usually contact the libraries directly and they will scan offline content for you for a fee.

Google Patents - Perhaps even better than USPTO Patent Search

USPTO Patent Search - Good for newer patents, cumbersome and "iffy" for patents older than 1972

USPTO Patent Application Search - I'm putting this here for posterity, no good for older applications.

USPTO Trademark search (TSDR - Documents)

USPTO Trademark Search (TESS - Much less reliable but shows history of ownership)

Newspapers.com - This site adds thousands of pages of content every day and, while it is a pay site, it is an excellent resource for research.

Ancestry.com - This site contains many documents that can't be found elsewhere such as City Directories, Census Records, etc.  This is a Pay Service.

Hathitrust.org - This is a fantastic free resource for deep dives into patents and trademarks, and other books, reference materials and so on that is usually locked on Google Books.  They hold all USPTO Gazzettes, and other patent/trademark documents.

archive.org - This has become a great source for information, particularly their "International Tool Catalog Library."