Nikon Nikkor-O 1:2.8 f=50mm for Bronica 6x6

In 1969 the older Nikkor-H 50/3.5 was replaced with the Nikkor-O 50/2.8. The new lens features a modern optical design which is half a stop faster and more compact that its predecessor. There are two versions which differ only in the lens coatings:
Single coated version:

Multi-coated Nikkor-OC: