I have several of the long bobbin machines, they're called shuttle bobbins. Then I have several Singer 66s which are round drop in bobbins. The real workhorses are the round vertical bobbins, yes I have several of those. If you ever need to clean and oil an old machine, go to 'quiltingboard.com to the vintage machine thread and look at Muv's video. You tube has a bunch of videos for more complicated work.
I love to tear them down, clean and oil, and make them sew like the champions they were made to be. Love them. Also want to hurt those people at the junk shop that are spray painting them with neon colors. I mean covering the tension assembly, the flywheel, bobbin cover, everything with thick coats of paint. Philistines! I hope the people buying those perversions drop them on their toes. (The old gals only weigh about 35 lbs.)