Within a year after x-rays were discovered by Roentgen, x-ray imaging was being used not only for medical applications, but also by Customs and Security people for examining the contents of packages and parcels. The full potential of the penetrating nature of x-rays with its ability to produce easily recognized images was quickly recognized, but its implication was impractical and proved less valuable for security use than for use in the medical profession. Hence, x-ray security systems faded away and were employed only on a very limited basis for about 70 years (1900-1970). During this period, manufacturers were offering industrial or medical x-ray units primarily designed for other functions. These machines failed to develop a viable market and no more than a few dozen units were actually employed in security functions. Even though the machines presented an x-ray image of the parcel, why did security officers avoid them?