This is I think a homemade tube sight. It is 36" long and has a Redfield adjustable aperature rear and will take Lyman 17A inserts in the front. In the picture the front knurled ring removed exposes the adapter for the Lyman inserts and the rear knurled ring levels the aperature.Here is a link comments appreciated.
http://smg.photobucket.com/albums/v126/garybehrman/Tube%20Sight%20by%20CW%20Behrmann/


gbehrman