old Portable sewing machine
If I was looking for a good old sewing machine, I would look for an older 830 Bernina or 1130 Bernina. Both are excellent machine and will last a lifetime. Singer made a few good old machine, but some had slant needle which I hate. I think you will have good luck with any brand as long as they are mechanical and were properly oil and cared for. If you are wanting a straight sew machine, look at the Singer featherweight, they are light to lift and store. Excellent machine for straight sewing.