New old stock Nikon lens replacement focusing ring, but unfortunately we don't know for what lens. Baggie it came to us in has the Nikon part # of 13680-055-1 but we don't know if that is the proper number for it. No results with an internet search on the number. All that being said we think this is likely for a lens from the Nikon F/F2 period as the ring has the scalloped look to it. Close focus is 2', 0.6m. Ring inside that would fit onto the focus helical is 55.7mm wide. Perhaps a 28mm f3.5? If anyone can tell us let us know.  

A fellow Ebayer has suggested this might be for the Nikkor-H 50mm f2.0. 

WHO WE ARE: Oddog2 is a husband/wife team, home-based small business specializing in the buying/refurbishment/selling of primarily photographic equipment. We do occasionally have other types of things to sell that come to us as a result of our search for camera-related items. We have 47 years of experience (22 years as a hobby, 25 as a full time effort) with photographic equipment, both as a shooter (17 years newspaper photojournalist) and as a collector/restorer/seller. We have been on eBay as Oddog or Oddog2 since September 1999.