I have no idea i am sorry. I have read about getting them reballed but cant be bothered. I have a PS3, and i dont get time to use that!
I believe one of them has a flashed firmware but i dont know which. They can be restored though to factory condition.
I got them from a friend, he said if i pay for them both to get fixed i can keep one and give one back, that was about a year ago. i asked him the other day and he said just keep them both.