2 pounds red boiling potatoes, scrubbed
2 tablespoons red wine vinegar
1/2 teaspoon salt
1/2 teaspoon freshly ground black pepper
3 hard-cooked eggs
1 small celery stalk
1/4 cup chopped sweet pickle (not relish)
3 scallions
2 tablespoons chopped fresh parsley
1/2 cup mayonnaise
2 tablespoons Dijon-style mustard