Nikon's fluorite 800mm f/5.6 — the F-mount super-telephoto flagship.
The Nikon AF-S Nikkor 800mm f/5.6E FL ED VR arrived in 2013 as the longest autofocus prime in the F-mount catalogue, built for bird, wildlife and motorsport professionals. It introduced fluorite elements and the electromagnetic diaphragm to Nikon's super-telephoto line and shipped with its own matched teleconverter.
The optical path holds 20 elements in 13 groups including two fluorite and two ED glasses with Nano Crystal Coat. Vibration Reduction is rated to 4 stops with Normal and Sport modes, focus runs from 5.9m via a Silent Wave Motor, and stops are set electromagnetically through an E-type diaphragm. It takes 52mm drop-in filters, weighs about 4590g and comes with the dedicated TC800-1.25E ED converter giving 1000mm f/7.1.
Against the 600mm f/4E it trades a stop and a kilogram for 200mm more reach, and the bundled 1.25x converter was matched to this lens alone. On DX bodies it frames like 1200mm, which keeps it the choice for small birds and distant subjects no zoom reaches cleanly.
Confirm the TC800-1.25E converter, hood, slip-on case and drop-in filter holder are present, as replacements are scarce and dear. Check the fluorite front group for pressure marks, that VR settles quietly and the foot has not been swapped without the original. Import examples should have UK-usable serial support.