In 1996, when Jacqueline Kennedy Onassis’ items went up for auction, it was such a spectacle that Sotheby’s issued lottery tickets to manage the crowds. Even the catalog itself has since become a collector’s item. So when one of the pieces from that sale resurfaced, Connecticut estate jeweler Betteridge jumped on the opportunity.  The brooch—centered on an ancient Greek gold coin from the time of Alexander the Great (about 330 B.C.) depicting Athena, the goddess of wisdom, nestled in an 18k yellow gold and emerald spray—was worn by the then–first lady on a trip to Athens. “Being able to so easily trace the lineage and the fact that she was photographed wearing it was an extraordinary thing,” says Win Betteridge, chief marketing officer for his family’s business. “For me that was the amazing significance. It was part of my dad’s personal collection. He had bo