Hi, ya'll! I've been away for several hours and I hardly know who to thank first! You're an amazing bunch. Glenn, the minute I read "can opener" that clicked, and I knew you were correct. It was smart of people to save and use a magnet like that because it wasn't always easy to find a good one in a store, and why pay money for something that you already had around? It sure looks like that fork could guide some thread or ribbon, too. All I'd have to do is put some duck tape across it to keep it from pivoting. Yel, it certainly does look like something that would attach, but the fork is too long. Anyway, I used to have a can opener with the same mechanism. There's a spring that allows the magnet to go down to the lid and then lift it when it's loose.
I'll be trying some tri-flow on the lid mechanism. The spring is attached, and looks to be in the right position. Nothing looks rusty, but there were more than 70 years worth of cobwebs in there, though the machine and table had been kept indoors in a clean house and were kept dusted. You have to remove a drawer to even see the mechanism. Maybe the spring has a little metal fatigue. I have not been able to pull or push the arm out by any method I tried, and can't pry the little button up. Don't know why it didn't occur to me to oil it. That was the first thing I did with the machine. The young woman who sold it to me said it was her great grandmother's and she had inherited it 10 years ago, but didn't use it. She needed the space.
I did a little googling and learned that this is the #42 style cabinet. There are no holes or even screw holes for attaching a pedal at the bottom or for the knee. Mine is missing the little seat that they came with, but I have an old piano stool that swivels and works well for me, though it looks rather out-of-place with the style.
Thank you to all who took the time to write!