Hi All, I've recently noticed some dark brown/black spots on the bottom back edge of my new-to-me 2007 Hot Rod '52 Tele (finished in 'thin skin' nitro). To be honest, I'm not sure if they were present when I bought the guitar (a few weeks ago) or if they've appeared more recently. I'm not too concerned with the marks themselves, they don't bother me. But I am curious about what the cause might be. And, if it's something that I'm doing, I'd definitely like to do something differently so that the problem doesn't get worse. I keep the guitar in its original hardshell case and I haven't played it with a strap since owning it.