Foreign Exchange The Diamond Dealers Club recently hosted Israel Week, which brought more than 100 Israeli ­dealers to its New York City trading floor for three high-spirited days of selling and buying. The idea for the Dec. 3–5 event came when Israeli Diamond Exchange managing director Moti Besser was talking to DDC president Reuven Kaufman at October’s World Diamond Congress in Mumbai. They eventually decided to bring a group of Israeli ­diamantaires to the United States and subsidize their hotel costs and other expenses. “Normally the cost to find new customers is very high,â