I bought a 6S of eBay, advertised as brand new. When it arrived it had no box however it has the plastic wrap etc around it and looked brand new. I contacted Apple to confirm warranty etc, they told me yes 12 month warranty, it had never been used but that it was a demo unit. What exactly is a demo unit? I got the impression of some time of phone they have on display in a shop for people to play with? But the phone is sim locked etc to a carrier and works fine.