Well, if you're not sure that to buy S3 on CL then pick a different site to purchase it. There's a lot of stores that offer best prices and based on my experience there's a lot of scams happening on CL, I was scammed before
my options for you is Amazon and MiniSuit. You can buy good quality 2nd hand items on Amazon well as on MiniSuit, they sell Original and brand new items with more products to choose from. I also but hard and leather cases there. Good luck!