reply to u/EdmundDante718 at https://reddit.com/r/typewriters/comments/1o5x527/missing_carriage_releases_on_scm/

It's incredibly common for these 6 series Smith-Coronas to have broken plastic carriage release levers (a major design flaw). You can call around to shops with parts machines for original replacements. https://site.xavier.edu/polt/typewriters/tw-repair.html

There are numerous YouTube repair videos and ideas including these few I've bookmarked before, though there are surely others: - https://www.youtube.com/watch?v=zNcQvfUk23s - https://www.youtube.com/watch?v=Gb9VlrKcXcM

I've not seen anyone 3-D print a version (yet), but designs for one might be floating around out there.

I've also seen people jury rig all sorts of plastic replacements which is an option as well.

In practice, you generally only need one working one for your dominant hand.