A photo posted on Slashleaks appears to show the rear shell of a glass-backed iPhone on top of a document referring to Ion-X glass. Ion-X is the type of glass used in the non-sapphire Apple Watch Sport screen, and while the SE hasn’t been specifically mentioned as a candidate for a glass-backed update, there has been no shortage of rumors about Apple going that way for its new iPhones. The case features what appears to be a camera opening that…