Lensfinder.com - Ultra Rare Nikkor 6mm f/5.6. Only a few hundred of these lenses exist. This lens has a 220 degree field of view for Full Frame 24x36mm sensors. Made in Japan
The remarkable Nikkor 6mm f/2.8 Fisheye - Japan Camera Hunter
Camera Geekery: The Nikkor 6mm f/5.6 Fisheye Nikkor aka The Holy Grail - Japan Camera Hunter
The remarkable Nikkor 6mm f/2.8 Fisheye - Japan Camera Hunter
Nikon Fisheye Nikkor 6mm f/2.8 Lens
The Camera Bag: Moby Dick-sized Nikon 6mm F/2.8 Fisheye Lens on Sale for $160,000+
Extremely Rare Nikon 6mm f/2.8 Fisheye Appears on eBay for $146,000 | PetaPixel
More Weird Lens News: Whale-Sized Nikon F/2.8 Fisheye Lens on Sale for $96K | Shutterbug
Deal of the day: Nikon Fisheye-Nikkor 6mm f/5.6 circular fisheye lens for $5,999 - Nikon Rumors
Nikon fisheye lenses FC-E8 and Nikkor 10.5mm
Deal of the day: Nikon Fisheye-Nikkor 6mm f/5.6 circular fisheye lens for $5,999 - Nikon Rumors