I've grown up (almost 70 now) with Hoover Type C bags in various uprights.
I bought a U4137 a few years ago but don't use it much. It did not come with bags. Stupidly, I tried to use Type C bags pulled down over the fill tube. What a mess!
I guess these vacs used a Type A bag? What's supposed...
Hoover Upright Convertible fans
I notice in your first picture, where the parts on your 707 are all laid out, the fan is an 11-bladed one, like the ones I've seen on other vintage machines. The newest replacements for my wife's model U4127 only have six. It looks like a generic replacement...