Ray wrote: Bought a 12 string in about 1964. It’s been hanging on the wall for at least 50 years but I’m sure it’s still playable!

Check the model. Some of those older instruments are valuable -- if they haven't suffered too much use.

But used 12-strings really don't last. Consider the Stella model that Lead Belly used. There is demand for them -- partly because it's what Lead Belly played, but mostly because so few of them are left. They're under-braced -- like all 12-strings with good sound.