3 cups coleslaw mix
3 tablespoons mayonnaise
4 teaspoons cider vinegar
1 1/4 teaspoons sugar
8 slices seeded rye bread
8 teaspoons spicy brown mustard
1 1/2 pounds thinly sliced pastrami
8 slices Swiss cheese, about 5 ounces, at room temperature
1/4 teaspoon salt