A closer peek at Naruto 455 at page 17....
Danzou has the Sharingan??!! a full normal sharingan??!!! (Hopefully he might have Mangekyou or not..)
My strongest guess would be that Danzo's sharingan could be Obito's right eye sharingan and it evolved to three slits just like Kakashi.... but in manga Obito's right side along with his Sharingan was crushed by earth and his body was buried in it.....
Post here if you have any ideas or reactions...