This is a support truss from the lunar module.
It is amazingly light. It must be close to (or even less than) one pound, but I don't have a scale that is that small. Comparing my body weight with and without the truss is negligible.
The truss is 21 inches long and 1 3/8 inches diameter. There is a very bold and clear stamp in red ink on both sides with part # LDW280-18847-19 A3.
Each end fitting is attached with 12 pieces of tiny hardware which are each sealed with a sealer. Curiously, it seems that each of the (24 total) hardware items are each individually stamped with a red inspector stamp (#621) and each of the main truss part number stamps is folowed by another inspector stamp #1459. The truss ends that are into the tubing are also cleanly sealed with some type of composite sealer.