updated 11:09 am EDT, Tue August 12, 2014
Could be pre-production part
Photos from well-known leaker Sonny Dickson show what is claimed to be a full back panel for the iPhone 6. The part is consistent with other recently leaks, although noticeably scuffed and dented. It appears to be a pre-production component, since it lacks printing such as the "iPhone" name and regulatory information.
One noticeable detail is a protruding ring around the rear camera lens, something not used on previous iPhones but which can be found on the fifth-generation iPod touch. If the part does reflect final design, it would be just another area in which Apple products have adopted cues from the Touch. That product, though, hasn't been updated since late 2012.
Apple should announce the iPhone 6 early next month. Recent rumors have pointed to a media event on September 9th.