Drain and flake tuna. Mix with celery, onion, relish, and salad dressing. Spread tuna mixture on 6 slices of bread; top with remaining slices. Mix eggs, milk, and vanilla. Dip sandwiches into egg mixture to coat each side. Brown in fat on a hot griddle or in a frypan, about 3 to 4 minutes on each side. Calories per sandwich: About 360