I have a few genuine Apple iPhone leather cases.  Most black or dark grey.  I'll have to double check what I have but I think there's cases to fit: 

 

SE, 7+, 6+, and 6.  All in good nick, with the original boxes.  

 

I've found these to be the best cases for the iPhone - the least bulky anyway.  Sure they don't give any front protection, but I've only ever cared about keeping the back scratch free.  Recently I discovered Pitaka cases and will be using them moving forward since I invested in one of their MagMount Qi's for the car.