A friend had this old Polaroid photo taken at the Washington Navy Yard in 1960. The bore measured 2.5 inches and of course there was no sign of any kind. This is one of a pair; I'd post the other pic but is only shows the center of the tube. These tubes are not in the Navy Yard nor in the museum now, but they could be in the remote storage site, who knows. The breech on this one looks like it must have had a bronze cap over it at one time, you just wouldn't put that out for troops the way it is in the pic, too hard to handle.
So exactly what is it?
