Nikon NIKKOR-H 50mm f/2 Black for Nikon S Mount.

Second hand, some signs of use but the glass is in excellent condition, no signs of fungus or haze. On close inspection there may be some dusts visible. The aperture ring turns smoothly.

By Ken Rockwell:

It's a bit softer at f/2, but cleans right up by f/2.8. It's sharper at most apertures than the 5cm f/1.4, which is as expected in this era. Back in the 1950s, people knew that faster lenses sacrificed optical quality for speed, and thus slower lenses were sharper.