Gerhard Fischar - Portable Metal DetectorIn 1925, Gerhard Fischar invented a portable metal detector. Fischar's model was first sold commercially in 1931 and Gerhard Fischar was behind the first large-scale production of metal detectors.
According to the experts at A&S Company: "In the late 1920's, Dr. Gerhard Fisher, the founder of Fisher Research Laboratory was commissioned as a research engineer with the Federal Telegraph Co. and Western Air Express to develop airborne direction finding equipment. He was awarded some of the first patents issued in the field of airborne direction finding by means of radio. In the course of his work, he encountered some strange errors and once he solved these problems, he had the foresight to apply the solution to a completely unrelated field, that of metal and mineral detection.