Oldest known sample of weapons-grade plutonium

According to Official Guinness Records,

A microgram sample of Plutonium-239 was produced using a 60 inch cyclotron at the University of California in Berkeley by a team headed by Glen T. Seabourg in 1941. The sample was stored in a cigar box until 1966 when Glen Seabourg and Emilio Segre presented it to the Museum of History and Technology at the Smithsonian Institute, where it resides today.

For a complete list of 1941 records, please visit 1941 Guinness Records in United States.

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