Interesting, I haven't come across any TG16s with burn marks like that. I can understand that lot of people are repairing broken consoles these days, but what kind of dumb ass puts down their hot soldering iron on the plastic case? They can't afford a soldering stand?
I have a Duo that looks like someone spilled acid on it. The top was slightly melted & wavy, with spill marks etched into the plastic.
Basically comes down to the fact that a lot of people don't take care of the stuff.