I can't say I care really. The Jazz I have is a USA Geddy Lee and it has his signature on the back. Granted, it isn't so much sharpie but likely just a decal and is covered by the clearcoat. ...but, either way, I'd just play it really. I can appreciate that Tony Franklin put his signature on the heel plate of his model so it can be swapped out but, if I had that, I would likely just leave it. No point, from my perspective of course, to spend money on replacing something that doesn't matter to me. On the other hand, if something happened to the heel plate and it needed replacing, I would't search the world over for a Tony Franklin plate either. I'd likely just get a basic Fender one. If my current bass had to be refinished due to damage at the signature, I wouldn't make a fuss about replacing the signature. I'd just get it refinished.