The casing in this picture was assembled after World War II, and it is considered the prototype for the original MK III. The original atomic bomb was tested at Trinity Site on July 16, 1945 without a casing. The 5,000 pound bomb was placed atop a 100-foot tower to simulate an aerial blast and reduce the amout of radio active dust spewed into the air. It was dropped on Nagasaki, Japan on August 9, 1945.
Weight: 5,000 lbs. With explosive surrounding plutonium core, total weight was 10,000 lbs.