Vivitar 28mm f2 MC Wide Angle Lens for Nikon AI -Bargain, Read-
This is a high quality metal built wide angle lens for Nikon AI. It is small with excellent image quality and would make an excellent general purpose wide lens.
There is a small line of coating wear on an inner element but I can only see it with a flashlight, it will not affect your images. The aperture is stuck open, likely due to oil on the blades. Shoot it wide open and get a good deal on a nice lens!