Large lens adapter in two parts, large outer barrel that looks to be bronze (?!) and smaller aluminum barrel that fits inside which slides nicely inside. From the size (OD of main barrel is 2-3/4", ID 2-1/2") and the spiral cuts on the outer surface it looks a lot like it would fit a large slide projector, perhaps a 6x6 or larger. Inner barrel is 2-1/2" OD, hole in center is 1". Inner aluminum barrel is not fixed in place nor does there seem to be any provision for doing so, like a thumbscrew, setscrew of some such. Weighs 2lbs. 

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.