Before it's opened, a pearl oyster offers no clues about the treasure inside. So imagine their delight when the folks at Paspaley Pearls found a perfectly round 20.4-mm rose-colored South Sea cultured pearl a few months ago. Executive chairman Nicholas Paspaley pronounced the pearl "unequivocally the most exceptional gem ever harvested by Paspaley Pearls and possibly the finest large pearl the world has seen during the past century." According to Paspaley, the pearl was harvested after spending two years in the oyster. When asked if the size was related to the size of the inserted bead nucleus, Paspaley said that in this case the two are unrelated. All of Paspaley's pearls are grown in the Pinctada maxima shell. The company is located along the northwest Australian coast between Broome in Western Australia and the Coburg Peninsula north of Darwin in the Northern Territory. "We always