I'm almost thinking that the Martin was some kind of dog that the museum had on hand but wasn't exactly "proud" of. I've seen plenty of old guitars that time and men have taken their toll on. Some to the point of not being able to be restored. We don't know if the movie prop was a parts guitar, a one-of-a-kind treasure, or just an average example of the breed.
What I do know is that Martin really likes to have their guitars seen on stage and screen as much as possible. They are in the business of selling new Martins. And a big part of that process is maintaining the Martin mystique. So if they don't care about Tarantino trashing one of their instruments making what will be at best a B movie hitting the Red Box shortly after it's theatrical release, why should I?
Tarantino: "CUT! Dammit, that is a priceless Martin!"
Russell: "Not any more."