The remarkable Nikkor 6mm f/2.8 Fisheye - Japan Camera Hunter
Ridiculous Nikon 6mm Lens Reappears, Priced at $160,000+ in the UK | PetaPixel
How can nikkor 6mm f/2.8 see behind itself?: Open Talk Forum: Digital Photography Review
6mm f5.6 Fisheye-Nikkor Lens
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