Preparations for the Trinity Project, the world's first detonation of a nuclear weapon; here one of the initiators for the bomb is delivered to the McDonald Ranch Assembly Room in a shock-proof case. The test, conducted on 16 July 1945 in the Jornada del Muerto in New Mexico, involved the Fat Man" atomic fission bomb of the type later dropped over Nagasaki, Japan. The device was triggered using an implosion method in which a slightly subcritical mass of plutonium was compressed to supercriticality by high explosives. The device weighed under 5 tonnes but had a yield equivalent to 20,000 tonnes of high explosive. Bloke in picture = technician Herbert Lehr"