WORLD WAR I POSTER World War I poster by L. A. Shafer, 39" x 29", depicts the crew of a German U-boat surrendering under the guns of an American destroyer as a troop ship sails past in the background. At top the poster bears the legend: "THEY KEPT THE SEA LANES OPEN" and at bottom the viewer is urged to "INVEST IN THE VICTORY LIBERTY LOAN". A fine image, in fine condition.