Weapon Courier's Message is a written note found in Dishonored.
Imagine the firepower of a tallboy but the speed and ease of concealment of a pistol. With this new technology any soldier with a steady gun-arm will be a force to be reckoned with. Make sure it gets to the Lord Regent without delay.
It can be found in the Flooded District, near Daud's Hideout. After entering the Central Rudshore map, turn left toward the Commerce building. Directly ahead are the remains of a rail car. The note is inside, along with blueprints for explosive ammunition for the pistol if Corvo did not take them from General Tobias's Office in Dunwall Tower.