Royal KMM basic introduction
Looks like a post-war standard Royal KMM, sometimes best known as the machine used by Jessica Fletcher in the TV show Murder She Wrote (as well as the upcoming Jamie Lee Curtis reboot.)
Richard Polt has you covered for the manual and some repair manuals/information.
Some contemporaneous videos on use and maintenance may help.
As for ribbon replacement, try this video. The spools for the standard Royal typewriters (Ten, H, KH, KHM, KMM, KMG, RP, HH, FP, Empress, 440, 660, etc.) have a custom metal mechanism for their auto-reverse. The spools are known as the T1 (which is the same as General Ribbon part # T1-77B , T1-77BR, and Nu-Kote B64.) If winding on 1/2 inch wide universal ribbon onto them, remove the eyelette which isn't needed and may interfere with the auto reverse. If necessary, Ribbons Unlimited carries these spools or you can get them (and ribbon) from a local typewriter repair shop.
Ribbon purveyors: https://site.xavier.edu/polt/typewriters/tw-faq.html#q1. I prefer Baco and Fine Line for their spectacular pricing and quality.
Other known historical users of the Royal KMM:
- John Ashbery
- Russell Baker
- Ray Bradbury
- Richard Brautigan
- Richard Brooks
- Pearl S. Buck
- Johnny Carson (or possibly KMG)
- Norman Corwin
- Frank Herbert
- Helen Keller
- Murray Kempton
- Ken Kesey
- George Washington Lee
- Harper Lee
- Ursula K. LeGuin
- David McCullough
- Margaret Mead
- Dorothy Paraker
- Grantland Rice
- Georges Simenon
- Christina Stead
- Tom Wolfe