In 2077, during the rush to shut down Sierra Army Depot and move its personnel to the front lines, corporal Dixon lost his eye through an accident Though still alive, his eye was badly injured, and the medical staff believed it was best to surgically extract what was left of the eye and place it inside a container of bio med gel. The eye did recover, but the rush to evacuate the depot meant that it was accidentally left behind and never reattached to corporal Dixon. The Chosen One can use the eye on retinal scanners in the depot, allowing him/her to activate some of the facility's locked elevators. Clifton's eye can also be used to do this.
Found (with the Sierra Depot medical log) in a locker in the first floor medical clinic.