Air service handbook
This is a 1918 military training manual from the United States Army Signal Corps, published in Washington, written to instruct aviation personnel in aeronautics. The pictures are plain line diagrams of instruments and measuring setups: a compass card with compensating magnets, a pointer gauge on a rod, a wing-like plan with lettered points, and a plumb-line over a circular float. A designer could take from them the clean, technical schematic style of early wartime instruction drawings, with lettered callouts and dashed construction lines.
