Place the eggs in a small saucepan and cover with cold water. Bring to a boil, cover with a lid and turn off the heat. Let the eggs sit in the hot water for 15 minutes. Rinse under cold water to cool, then remove from the shells, finely chop and add to a medium bowl.
Mix in the mayonnaise and capers until well blended. Stir in the parsley, olives, celery and apples. Drain the tuna from the oil, then fold into the dressing. Taste for seasoning and add salt and pepper to taste. (The capers and olives are salty so be careful not to over-season).
Slice the baguette down the center into 2 pieces using a serrated knife and slice across into 4 equal pieces. Scoop tuna salad down the center of the bread, top with lettuce and sandwich with the top pieces of bread.