These should be officially graded products. A hifi dealer might sell their stock as ex demo but that’s something different. The graded units are assigned a new part number which distinguishes them from the original. You will see this on the box (New labels), and it will be updated in the computer system at the factory. The origin could be for example a faulty unit that has been returned from a dealer via rma but has been sent a new one out. So the returned model gets serviced and depending on the finish might get graded as a/b/c. The units will function perfectly but will be cosmetically imperfect in some way. Grade A you’d be hard pressed to find a fault.