Building a Royal O model
The two subjects in question were two Royal Os in gloss black, the first of which was missing all feet, the spacebar, the entire constitution of the carriage besides the frame, and had (as I discovered) a bent rack. The bent rack caused the carriage to bind on the escapement pawl. The second O was missing the carriage entirely, which was situated off to the side in a heap. It was also missing the bell striker and the rear carriage rail, as well as the shift bearings.
My first assessment told me that the one with the intact rails would be easiest to fix, so after cleaning up the bulk of the machine, I began the cleaning and transfer of parts based on aesthetics, and selecting only the ones I felt looked the best. This included a brand new set of feed rollers.