5200mm Canon Lens World's MOST powerful Super telephoto EF FD (updated upload) / Inventions

Canon 5200mm F14 Prime Lens. The world's largest dedicated SLR Super Telephoto lens. Extremely rare. Made in Japan. Most probably a government ordered cold war spy tool - it certainly wasn't designed to look at the stairs with the use of it's ND filters... It uses a mirror & lens combination. The front lens is massive.