While vintage razors are generally high quality, as with most things, there are good and bad brands and models. The best vintage razors were produced by Gillette from the 1940s to the 1970s.
Don't be afraid to buy a really scummy old razor! Certainly people used these kinds of razors back in the day for shaving body hair, but are they preferable to modern models? I have a BEAUTIFUL early 1900s razor that practically eats my legs. I have used my guy's mini vintage razor on my armpits, and I like it.
This type of razor should always be adjusted with the blade doors open, then close the doors on the blade afterward.