The shopgirl at Jacob & Co. advised me to browse until I found the ring that called out to me. After squinting into countless glass cases, I found a stunning 4.95-carat baguette-diamond ring that looked straight out of To Catch a Thief. With an eighteen-karat-white-gold band and two diamond loops, the ring was dazzling enough to wear with anything. Granted, the diamonds were large, but they were restrained by Jacob's standards. 48 E. 57th St., nr. Park Ave.; 212-719-5887.