Hi everyone. My mother has an old sewing machine that belonged to my grandmother and she has decided she wants to start using it again. It works mechanically, but nobody in the family knows how to thread it properly or what the various attachments in the box actually do. There is no branding on it beyond a name and a serial number. Is there anywhere that documents machines this old, or is this a lost cause and a job for a repair shop? She is in her seventies and not confident with computers, so I am doing the searching for her.

Not a lost cause at all, sewing machines are one of the better documented categories because so many survived and people kept using them. The serial number is your key, on most makes it dates the machine and identifies the model family. ManualMachine https://manualmachine.com/ lists the main sewing brands including older machines, and threading diagrams are usually in the user guide rather than the service document. Worth checking whether the attachments are original to that model, boxes get mixed over generations and half of them may belong to something else entirely. Since you are doing the searching, print the threading diagram rather than showing it to her on a screen, it is far easier to follow with the machine in front of you.