I owned a black M65 several years ago that was almost in mint condition and was a beautiful guitar. Sadly, the action was too high and could not be adjusted at the bridge (bridge top was already all the way down and resting on the bridge bottom).
My luthier told me that the neck block was very shallow (short) compared to a guitar like an X-175 and the string tension had pulled the neck into the body. He said it happened a lot on hollow body thin line guitars like a Gibson ES 125 T (T for thin line).
He had two fixes: reset the neck with some cosmetic damage, or heat-treat the neck and pull it back to where it originally was. I asked him if there would be any damage to the nitro finish with a 'heat treat' and he laughed and said, 'Well, yeah!'
So Pitt, look at the guitar closely before you buy it. Make sure the neck doesn't look like it's diving into the body and that the bridge isn't adjusted all the way down but you still feel like the action is too high for you.
Another symptom is that the truss rod may have been adjusted to make the fingerboard as flat as possible in order to make up for the the action being too high at the bridge. The way to check the truss rod adjustment is to first hold the low E string down at the first and last frets and see if the fingerboard is dead straight from a side view. Then repeat the task by holding the high string down the same way and checking for flatness. There should be some relief in the fingerboard. If the strings are dead flat on the fingerboard and the action is still too high, then you have a problem.
Oh, look at the crown of the top from the side and see if it looks like the top is flattening out or caving in around the bridge, the pickup hole, or the f-holes. That happens on a laminate top guitar. Sometimes it's just a bit (acceptable), sometimes it's a lot (thumbs down).
$1300 is a premium price. I sure would be happy about everything on the guitar before I dropped that much cash. And if words & terms like 'relief', neck-dive, heat-treat, etc. don't mean anything to you, take a friend along who knows better. See if you can pay your repairman to go with you. I'd a lot rather pay the luthier $40 bucks and buy him a good lunch, then decide not to buy the guitar based on expert advice, than pay $1300 without an experienced opinion and regret the purchase.
Good luck!