This is a 67mm adapter ring, for use with the Nikon AF-3 filter holder.
Urth 86-67mm Adapter Ring for 100mm Square Filter Holder
Nikon 72mm Adapter Ring for AF-4
Nikon 62mm Adapter Ring for AF-4
Nikon 52mm Adapter Ring for AF-4
Nikon 77mm Adapter Ring for AF-4
Nikon SY-1 67mm Adaptor Ring
