First Claimed Images of iPhone 5S Rear Shell Surface - Mac Rumors
The part is extremely similar to that from the iPhone 5, in line with Apple's pattern of maintaining a given body style for two generations before making more significant modifications. This iPhone 5S part is, however, distinctly different from its iPhone 5 counterpart in several ways, most obviously in the arrangement of the screw holes for attaching the logic board.
Comparison of iPhone 5S and iPhone 5 rear shells with logic board screw holes boxed in red
via macrumors.com