Only use the UPC number that already is on the item -- that UPC was specifically designated for just that one piece or series of pieces, manufactured at a particular time, at a particular place, by a particular manufacturer (that's the information that's buried inside all those lines & numbers).
And please don't add a UPC number to an item that never previously was manufactured with a UPC number -- the old item specifics on the item may not match the designated specifics on the UPC. Too many eBay sellers are adding UPC & ISBN codes to items that were never originally registered with UPC & ISBN codes, and many of those items now reflect incorrect data -- an easy ticket to "item not as described" land!
