Like the dummies mentioned above, this shell features two distinct antenna breaks at the top and bottom, rounded corners, a circular cutout for the LED flash, and a larger overall size than the current iPhone 5s. The case appears to be covered in a protective plastic coating, but a bit of silver coloring is visible between the flash and camera cutouts, indicating that this could be for the sliver phone model.
Read more at http://9to5mac.com/2014/05/29/iphone-6-rear-shell-reportedly-on-display-in-new-leaked-photo/#BMK6R65tUjlT0Vm3.99