Description: For 4.5″ barrage rocket. Designated by the navy as Mk137. 2.965″ long, brass and steel. About 42,000 manufactured by Caltech for the navy in 1943. Prototype for several later fuzes. “A”: cutaway model with 10-vane propeller. “B”: standard model with 8-vane propeller, cutaway. “C”: Model 2, 10-vane propeller; minor alterations over the original model were made by the Bureau of Ordnance (Buord).