For 78 years, this slender Flatiron joint has dished out diner fare like hot dogs and egg creams with the kind of (earned) swagger unique to New York’s restaurant institutions. Workers from nearby offices and the inevitable clutch of tourists have edged out the over-60 set, but locals still sidle up to the counter for retro classics. The corned-beef-and-chopped-liver sandwich and the spectacularly cheesy Reuben belong in the pantheon of the city’s deli stalwarts.