KEH used to charge more for the Nikkor-O version compared to the multicoated version. I asked- was told many photographers preferred the look of the single-coated lens.
I've had mine for almost 40 years, had Mora camera convert it to Ai with a factory kit. Sold the 35/2 Ai version, kept the converted Nikkor-O.
Just to add: the 35/2 Nikkor-O was reformulated early on: the first version is not as good as the second. I'm not sure of when the change-over occurred, mine is the second version.