This is a World War ll B17 bomber oxygen tank. This one was described as a walk around tank and was used by the airmen during World War II as they walked about the bomber. It is a very unusual size as most World War II oxygen tanks are short and fat. It is in absolutely excellent shape with the coolest patina. I am not sure if it is stainless steel or aluminium. It measures 24" across in 6" high. $135. If you have any questions you can call me at 909 797 1932. Thank you, Dave.