Not that it's too important for us here, but the Lusitania was running only three of its boilers on its last crossing. If only all four stacks were spewing smoke and steam, the German submarine would not have arrived on time to sink her.
codex, is that a ship board postmark? (I can't make out any of it.) I see the envelope is marked "late," so I'm assuming it made it to the ship at the last moment.
P.S. During the war, the Lusitania used to pick up mail from British picket ships at the edge of international waters. These ships remained at sea to ensure that interned German ships did not try to make a run for it out of New York.