Please don't bump like this, its against forum rules. No replies means no-one has had anything useful to add.
Its up to you to correlate the magsafe with the laptop concerned for warranty, if you were to claim an old magsafe using the warranty for a new MBP I don't know whether that would be obvious to Apple, the Magsafes have chips determining which works with each so they can tell the charger is the correct technology for the serial or not but beyond that who knows....