This is a Nikon HB-11 Bayonet Lens Hood designed for the AF Zoom-Nikkor 24-120 F/3.5-5.6 lens. It is made in Japan and has a twist-on fastening mechanism. The circular hood helps to reduce lens flare and protect the lens from damage.
Like all of Nikon's lens hoods, this is made well and fits the correct lens it was made for, precisely. It protects from the sun's glare the way it should. Keep in mind though, if you are using a camera with onboard fill-flash, remove the hood. The flash will impact the top of the sun shade and show a dark area on that part of the photo.