Module 8 Optics - 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
Extremely Rare Nikon 6mm f/2.8 Fisheye Appears on eBay for $146,000 | PetaPixel
8mm f/2.8 Fisheye-Nikkor AI
Nikon's 6mm f/2.8 Fisheye on a Z 9 - first time ever?