In a large skillet, melt 2 tablespoons butter over medium heat.
Add the coleslaw, vinegar, salt, sugar and pepper. Cook until the coleslaw is wilted, stirring frequently, 5 minutes.
Spread each slice of the marble rye with Thousand Island dressing.
Layer the turkey evenly over half of the bread slices; top each with 1 slice Swiss cheese. Spoon the coleslaw mixture evenly over the cheese. Cover with the remaining bread slices, dressing-side down.
Spread softened butter over the bottom and top slices of each sandwich. Grill the sandwiches until golden brown, 4 to 5 minutes per side.