During the '40s in the United States, the shoe fluoroscope was very popular in shoemakers' stores, but it hid a terrible secret.
This machine emitting X-rays allowed to observe the state of the foot inside the shoe and the perfect fit.
The first versions date back to the First World War, used by doctors to diagnose the wounds of soldiers without removing the boot.
In the following years, the machine was perfected, improved and even patented, as in patent US2315149A.
Of course, once the serious side effects of X-rays were discovered, commercial use was banned.