I just finished repairing a 1939 Corona Zephyr. I hadn't had a close look at one of these before. It's a cute little portable—Smith-Corona's answer to the Hermes Baby—and the basic mechanism survived into the 1970s on various Smith-Corona products, even including some electrics.
Compared to its better-known successor, the Skyriter (introduced 1949), the Zephyr has more charm, for my taste, thanks to its round ribbon spool covers and round keys. But it has one major disadvantage: whereas the Skyriter is about the easiest typewriter ever to remove from its shell (just remove two screws and pull the mechanism out from the back), the Zephyr requires you to remove 6 little screws and then squeeze the top row of keys under the frame, which is a challenge. Reassembly is just as hard.
But it was worth disassembling the typewriter in order to give it a good cleaning, and also because inside it I found this index card. It must have been inside the typewriter a good long time. Since it's written with a fine-point fountain pen, it probably predates the popularity of the ballpoint, which began its rise after World War II.
Presumably the owner of this typewriter was a student who was studying vocabulary. I find this particular mini-thesaurus very appropriate.
When you're working on a typewriter, note the details; notice, mark, and realize what's on it and inside it. Your observation and reflection will bear fruit when you heed, regard, and study what you find. Scrutiny pays dividends when you observe, contemplate, scan and consider your discoveries.
Typewriters help us pay attention when we write, and typewriter maintenance is also an exercise in focus and observation.