An old safe buried in a waste trench at the Hanford Nuclear Reservation in Washington State has yielded an artifact from the birth of the atomic age: a batch of plutonium that is among the first ever made.

The plutonium, found in a one-gallon glass jug after a cleanup crew tore open the safe with an excavator, was processed at Hanford in late 1944 from spent uranium fuel from a reactor at Oak Ridge, Tenn. It was the product of test runs of a plant built for separating plutonium for use in the Manhattan Project to build the atomic bomb.

Apart from the historical significance of the discovery  the only earlier sample of man-made plutonium known to exist was produced in 1941 in an accelerator and is stored at the Smithsonian Institution  the techniques employed to determine its origins provide a glimpse of the kind of detective work that might be used against atomic terrorism.

“This is a completely unclassified example of the type of science you could apply in nuclear forensics,” said Jon M. Schwantes, who led a team that analyzed the plutonium at the Pacific Northwest National Laboratory in Richland, Wash. Their findings were published in Analytical Chemistry.