This is a 77mm adapter ring, for use with the Nikon AF-4 filter holder.
Nikon 72mm Adapter Ring for AF-4
Nikon 67mm Adapter Ring for AF-3
Nikon 62mm Adapter Ring for AF-4
Nikon 52mm Adapter Ring for AF-4
Tiffen PRO100 Adapter Ring 77mm
Kase 77mm Magnetic Circular Adapter Ring
