The history of these machines was very interesting. Watched the Treadle Lady's youtube videos as well - doesn't seem complicated. Thank you for the links!
I decided I needed to step back and assess. I never figured on becoming so fascinated with these machines! The Bel Air machine was an impulse buy, and I do try hard to avoid that. That said, I am glad I purchased that one.
And - she will need a bit of work before I can use her.
My original plan was to get a 15-91 (which I now have), a treadle someday, and then yet another machine - had gone back and forth between thinking a 201 or maybe a 301 or 401. Hand crank was not in my plans. I want to be able to use all of my machines. And - now that I have 4 sewing cabinets sitting up in my sewing room - I also have to realize my space limitations.
So, the same day I happened upon the hand crank I also went and saw a 403. Loved it! Decided the 403 was immediately of more use to me and will pick that one up next week. Have it half in my mind that if the hand crank is still there in a few weeks, maybe it is meant to be and I will get her. While I am intrigued by the vibrating shuttle, I think I would rather stay with round bobbins. And if I had to choose between a hand crank and treadle, I do believe I would choose treadle (though I realize I can treadle a hand crank).
There are so many different machines out there! I realize I have just begun to scratch the surface. If she and I somehow end up together - I will definitely post!