The Deepdene gets its name from the Pennsylvania estate of Margaret Adams Plummer, wife of Curtis Bok, both the diamond's original owners.
Its clarity was stated as VVS1 (with two very small imperfections near the girdle or midsection of the stone) and its vivid-yellow colour was guaranteed to be natural by both the German gemological institute and the University of Mainz.
Gübelin's experience with examining gemstones and recognizing artificially colored diamonds led him to declare that the Deepdene had been irradiated, likely by neutron bombardment.
[citation needed] Gübelin warned Christie's and any buyers who would listen, but the sale was allowed to continue with the recommendation that the stone be examined by another lab.
[citation needed] After being sold to jewelers Van Cleef & Arpels for a reported £190,000 (about US$460,000 at the time), the Deepdene was sent to the Gem Testing Laboratory in London, England.