Passive x-ray and gamma-ray analysis was performed on UC Berkeley's EH&S Sample S338. The object was found to contain Pu-239 and no other radioactive isotopes. The mass of Pu-239 contained in this object was determined to be 2.0 +- 0.3 micrograms. These observations are consistent with the identification of this object being the 2.77-microgram plutonium oxide sample described by Glenn Seaborg and his collaborators as the first sample of Pu-239 that was large enough to be weighed.
Cite
@article{arxiv.1412.7590,
title = {Seaborg's Plutonium?},
author = {Eric B. Norman and Keenan J. Thomas and Kristina E. Telhami},
journal= {arXiv preprint arXiv:1412.7590},
year = {2015}
}