Better built than most of today pro lenses this little gem was one of the E Series glasses.
This series has been produced by Nikon in the ’70s to compete in the market with a bunch of low priced lenses (“E” stands for “Economical”).
Nevertheless a few of this glasses have become jewels. This 100 Ai is one of them.
It is as sharp, or often sharper, than the 70-180 Micro Nikkor, a great lens per se. But the Micro Nikkor costs 1200 USD or more, while the 100 Ai 100 USD in mint condition.
If you find one get it, except if you shoot portraits; in this case the 85/1,8 will better fit your needs because the largest maximum aperture.