I know nothing about older machines in general, I just wanted to add my two cents worth about the treadle. Having a person-powered machine is a HUGE selling point to a certain segment of the sewing and quilting population.
I have a friend whose 93 year old mother died. She had an old hand-crank Singer that he inherited. He thought it was garbage because he couldn't imagine that anyone would want a machine that's not run by electricity. He was going to take it to the dump. I just about had a heart attack. Practically yanked it out of his hands, cleaned it up, took good pics, sold it on FB Marketplace for $200. He was blown away when I gave him the cash. There are a LOT of people who sew in RVs, long-haul truckers, cabins-in-the-woods, etc who are looking for non-electric sewing machines.