How do you tell the difference between the Professional and Generation II pans? I have a host who has a 12" skillet that's warped. If it's a Professional, it's still got a lifetime guarantee, right? Even if she doesn't have her original receipt?I just don't know how to tell what kind it is. I haven't seen enough of either line to know.She and hubby are buying a whole new set at 60% off, I just don't want them to have to use their 1/2 price item to buy a new skillet if they can get this one replaced for free.