You won't know, the guys in the stores or repair centres probably won't know either; Apple in the warranty conditions reserve the right to use remanufactured or refurbished parts. But there's no way of telling for any specific part really, they have the same part number, regardless of if it is a "new" one or a "remanufactured" one. My experience with stuff I've had repaired is everything seems good, looks pristine, etc.