The Micro-Nikkor 55mm f/3.5 AI, is considered one of Nikons sharpest lenses. The AI version of the Micro-Nikkor is like you might expect of an upgrade of the Pre-AI version. It shares the same optical formula of five elements in 4 groups. The only difference between the Pre-AI and AI version is the AI spec. You have to go back to the 55 f/3.5 Micro-P.C to see a difference between the lenses, at least as far as the look of the lenses goes.
Nikon made several different cosmetic versions, both AI and non-AI with the same optics, both single and multi-coated.
These versions are best identified by serial number, or more casually, by a rubber (not fluted aluminum) focus grip.
Nikon made about 500,000 of these later versions; about 275,000 AI and 165,000 non-AI.
Also please check out my other listings as this is one of a set from 1977.
Specifications
Lens Construction: 5 elements in 4 groups
Picture Angle: 43° (35mm)
Minimum focus distance: 0.241m
Filter Size: 52mm
Lens Hood: Screw-in HN-3
Size and weight: dia.66 L55 245g
Diaphragm: 6 blades