Nikkor-H 1:3.5 f=5cm Nippon Kogaku Japan for Bronica 6x6

An early wide-angle lens, introduced for Bronica 6x6 cameras in 1958. This lens has many parallels to the F-mount Nikkor-H 2.8cm (28mm) 1:3.5 made at the same time, with similar angle of view, same speed, and probably based on a similar 6-element optical design. There are two variations:
Early lens marked in cm with dots on aperture scale:

Late lens marked in mm and no dots on aperture scale: