Nikon Nikkor 8mm f/2.8 Fisheye Lens F Mount - Rare AI Version Fisheye-Nikkor

Thoroughly tested, externally cleaned and sanitized. In perfect mechanical condition and working order. AI version, wich seems to be the rarest among non-AI and AI-S. 
As shown in the photos, the item is in good overall condition; it exhibits some general sign of usage, like scratches and minor paint loss.
The lens is clear, totally clean from fungus, haze or significant dust. Shows no coating degradation. The front element shows some scratches, mainly located near the bottom left border of the lens, that seems not to affect image quality at any aperture settings. 
The internal filter turret works flawlessly. The AI version have L1Bc, Y48, Y52, O56 and R60 filters, same as the AI-S. 
What's Included: Fisheye-nikker lens, caps

Pre-owned item. Sold under the margin tax scheme (0% VAT applicable). A business invoice can be issued upon request, please provide your company details immediately after purchase. VAT may still apply at delivery for extra-eu customers.

Nikon Fisheye-Nikkor 8mm f/2.8 AI — a legendary circular fisheye lens engineered for Nikon's manual-focus F-mount system. Delivering an extraordinary 180° angle of view, this optic renders the full hemispherical circular image characteristic of true fisheye design, distinct from full-frame fisheyes that fill the entire sensor.
Built during the AI (Automatic Indexing) era, it features Nikon's classic all-metal construction with a built-in rotating filter turret, housing five internal filters (L1BC, O56, Y48, Orange, and Red) selectable without removing the lens — a hallmark of Nikkor fisheye engineering. The recessed front element is permanently integrated into the lens barrel, a defining trait of ultra-wide fisheye optics of this generation.
Optically composed of 8 elements in 5 groups, it offers a minimum aperture of f/22 and manual aperture control via the classic AI coupling ridge, compatible with both metered and non-metered Nikon F-mount bodies. Focusing is fixed near-infinity due to the extreme depth of field inherent to fisheye design. A favorite among architectural, scientific, astro, and creative photographers seeking dramatic curvilinear distortion and immersive perspective, this lens remains a benchmark in vintage Nikkor optics and circular fisheye photography.