The first notable difference of course for the general shape of the map but not really enough to jump to the ceiling. Even more interesting, a mysterious square element placed closer button instantly revives the rumor. Followed by two other components attached to the extension of the map and that all seemed to be resistance. Needless to say that these three elements are absent from the button back to the home of the iPhone 5 and is to my knowledge unprecedented for this spare parts, all iPhone generations combined.
The part is identified with number 821-2092-01 which is in line with Apple's usual number scheme and it appears to have been manufactured in the 29th week of 2013 (mid-July).
Notably, MacRumors spotted the same part being sold as a iPhone 5C home button on sw-box so its a bit unclear which device it belongs to.
Apple is expected to unveil both the iPhone 5S and iPhone 5C on September 10th.
Take a look at the photos below...