in the 1940s and 1950s, x-ray machines were used in stores to help sell footwear. these were known as shoe-fitting fluoroscopes. however, as the harmful effects of x-ray radiation were properly considered, they finally fell out of use. shoe-fitting use of the device was first banned by the state of pennsylvania in 1957. (they were more a clever marketing tool to attract customers, rather than a fitting aid.) together with robert j. van de graaff, john g. trump developed one of the first million-volt x-ray generators.