This is quite the update - very sleek. My favorite new feature is the "show on hover". Just put your mouse where the icons should be and the appear like magic!
It really cleans up an already improved menu bar in macOS Big Sur.
We use HelpDocs.io (love it) and they have a "set article to go stale" option. I haven't used it, but it seems like a nice reminder to re-evaluate or delete the page.
What a great project. I have a very similar book (1800 Mechanical Movements, Devices, and Appliances) and have a blast flipping through it. It is great to see the illustrations come alive. Great great job!
There are actually a great many of these "mechanical movement" books from that time period, circa 19th to early 20th century.
They are contemporary with similar books on "electrical machinery" (generators and motors, mainly), "steam engineering", "home and farm improvements/implements", and many other similar subjects.
Some were aimed at the professional engineer, while others were meant or accessible to the ordinary person with such interests or needs.
I enjoy discovering and adding these books to my collection when I can find them at used and antiquarian bookstores.