https://www.reddit.com/r/typewriters/comments/56p9zt/royal_quiet_de_luxe_backspace_fix/

https://www.youtube.com/watch?v=iW_KWF7wcfs

https://www.reddit.com/r/typewriters/comments/1hk0ebb/smithcorona_escapement_noise/

https://www.facebook.com/groups/1134879143309729/posts/3544203715710581/

Jeweled main bearing on the escapement is what Smith-Corona is talking about in their branded "Jeweled escapements". (2:26)