I found an old Griswold at an estate sale last month with heavy surface rust, no visible cracks, smooth original machined surface underneath. I took it home, and did the electrolysis bath, re-seasoned four times and it's now one of my best pieces. The rule I use is: surface rust is never a reason to walk away and pitting is where you have to decide. Light pitting you can usually cook through, it'll fill in over time. Deep pitting and structural damage is a different story. What condition do you use as your walk-away point?