Title supplied by cataloger based on information from sheet label. Image is a photoreduction of the mosaic created from original aerial photographs. Designating symbol DH. Form of individual image numbering: DH-1A-[number], DH-2A-[number], DH-3A-[number], or DH-4A-[number]."Flying completed 7-13-40." Flown by Aero Service Corp. Philidelphia, Pa. "Approximate scale, 1:20,000" [refers to individual images from which mosaic was made].
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