How to identify a refurbished Iphone 6s

Hello everyone!..I am from India and am going to buy an Iphone 6s from an e-commence website.I know in most cases the seller ships a new phone.But rarely they ship a refurbished phone labelling it as a new one.

Could anyone please enlighten me on how to identify if I received a NEW IPHONE 6s or a REFURBISHED ONE ..

Thanks in advance.