Stock Photo - A Thornton-Pickard 'Photo Gun' Mk IIIH on display at the Montrose Air Station Museum in Scotland. These were used for aerial reconaissance in World War I by the Royal Flying Corps -- Picture by Jonathan Mitchell/Atlas Photo Archive.

Stock Photo: A Thornton-Pickard 'Photo Gun' Mk IIIH on display at the Montrose Air Station Museum in Scotland. These were used for aerial reconaissance in World War I by the.