Quote Originally Posted by kitanikon View Post
The "K" version of Nikkors are COSMETIC updates with rubber covered focusing barrels...there were several versions of the "K" series....

....some were updated cosmetically (rubber covered focusing barrel, different front lens barrel, some with built-in hoods some not) with no change in optic design...Nikon offered AI aperture rings as an option for these lenses (and for some of the pre-K versions as well)
....some were updated optically when the cosmetics were revised...though NOT yet AI converted with the AI aperture ring...that were offered (as above) as an option
....some were updated optically, cosmetically, AND with the AI aperture ring....

And of course some continued to be updated after becoming AI lenses....

The 135/2.8 went through ALL 3 of these iterations...from the "Q" to the "Q-K" to the compact non-AI-K, and the compact-AI-K

The 50/2 "K" came out before the AI version...having the same optics but without the AI aperture ring...lacking the AI aperture ring makes it less valuable to users of Nikon dSLR bodies that require the AI aperture ring (though it can still be used on many though not all lower end Nikon dSLRs, eg D40, 5100)
Ah, OK thank you. I have what may be a "K" version of the 55/3.5, with the rubber focussing ring, non Ai, non multicoated.

I had been calling these lenses "RIFR" for rubber insert focussing ring. My understanding is that the lenses marked C as in "Nikkor H-C" are multicoated?