The Gallaudet D-1 was a complex machine - not only the propeller was mounted amidships, but also two Duesenberg engines side by side. It was first assigned early USN serial AH-61, later 59A. It did well enough apparently to be assigned to seaplane launching trials conducted by the cruiser Huntington in 1917. It was followed by the D-2, with the observer seated in front of the pilot, and the D-4 with a single Liberty engine. Photo from: National Museum of the US Navy