From the 1920s into the 1970s, shoe stores invited children to step onto a polished wooden cabinet, slide their feet into a slot, and watch their own toe bones wiggle in glowing green through one of three viewing portholes, one each for the child, the parent, and the salesperson. This episode tells the story of the shoe fitting fluoroscope, also sold as the pedoscope, and the patent squabble behind it: Boston physician Jacob Lowe sold his rights to the Adrian Company of Milwaukee for $15,000, the Adrian family claimed Matthew Adrian built the first machine, Clarence Karrer said his idea was stolen, and a St. Albans company patented the British Pedoscope in 1924.

The numbers are startling. A typical 20 second viewing delivered an average of 13 roentgens to a customer’s feet, and some American machines measured up to 116, while scattered radiation leaked sideways at pelvis height into the clerks who stood beside them all day. A 1948 evaluation found the machines useless for fitting shoes, yet the industry argued they prevented bunions and corns. By the late 1940s about 10,000 were running in the United States. The FDA acted in 1953, Pennsylvania banned them in 1957, the United Kingdom settled for a warning sign in 1958, and Switzerland held out until 1989.

• Why children trying on three or four pairs in an afternoon took repeated doses while being about twice as radiosensitive as adults
• A shoe salesperson’s 1950 radiation burn that ended in amputation, and a 2004 report of basal cell carcinoma on a former clerk’s sole
• Hermann Joseph Muller’s 1927 discovery that radiation causes genetic mutations
• The 1946 suggestion that children use the machines no more than 12 times a year
• A working machine spotted in a Boston store in the late 1970s and Time’s 1999 list of the century’s worst ideas