The pedoscope was a modified medical device consisting of a metal box, covered by wood and with a series of viewing portals.
Marketed to shoe shops in the early-20th century, it claimed to enable sales assistants and customers to take a detailed look at the fit of a pair of shoes. The customer would place their feet inside the box, between an X-ray source and a fluorescent screen.
The feet were exposed to X-rays for about 20 seconds, and absorption by the foot bones and the shoe materials cast a shadow on the screen, forming a moving image.
In reality, the pedoscope was of very little use in selecting a good pair of shoes. The calcium in bone absorbs most of the X-rays, but the soft tissues do not and therefore don’t show up very well on the screen. Without seeing the fleshy parts of the foot, fit was effectively being judged using bone structure alone.
Not only were the machines less effective than advertised, but they actually had the potential to cause serious harm. X-rays produce ionizing radiation, and the devices were often leaky, repeatedly exposing customers and staff to low-level doses of radiation.