$15 at an estate sale, I was definitely prepared to pay more. I've seen people finding such cool stuff at secondhand shops and had no luck myself, so I'm hoping I can get some life out of these.
Also got a plane (one of the adjustments doesn't work but otherwise looks decent) and a Heath Kit power supply.
This looks super detailed. Of course, I couldn't say if the guy is confidently bullshitting us, but it looks like he knows his stuff https://youtu.be/7UEAoh2I1Lk