reply to u/Novembree at https://old.reddit.com/r/typewriters/comments/1hfncyz/had_a_typewriter_for_awhile_could_use_help/
Welcome to the Royal KMM club! Seems like lots of these have been posted in the last day including one by u/betternatured and another by u/the-other-gusta along with a very similar Royal KMG by u/Jacki-san.
The serial number puts yours down as a KMM with an 11 inch platen manufactured in 1945. Cross reference: https://typewriterdatabase.com/royal.72.typewriter-serial-number-database
Manual: https://site.xavier.edu/polt/typewriters/RoyalKMM.pdf
These were really popular and ubiquitous, standard (large desktop) typewriters in the mid-century that were the workhorse of many offices. Because they were so common and so heavy, they only go for $5-25 in the used market in either unknown or marginal condition. If they're cleaned up and well-serviced they can go for more with a cap of around $300-400 depending on the level of restoration. Some with special features (like special typefaces) or provenance may go for more.
The Royal KMM was known to have been used by writers including: John Ashberry, Harry Ashmore, Russell Baker, Ray Bradbury, Richard Bratigan, Richard Brooks, Pearl S. Buck, Johnny Carson, Norman Corwin, Frank Herbert, Ken Kesey, G.W. Lee, Harper Lee, Ursula K. LeGuin, David McCullough, Margaret Mead, Grangland Rice, and Dorothy Parker. This was also the model famously used by Angela Landsbury's character on the TV show Murder, She Wrote.
Depending on your level of typewriter knowledge try out some of the following short films which will also provide some tips, tricks, and maintenance advice common in the era of your machine:
Happy Typing!