Do you remember these things? When I was growing up almost all shoe stores had one. It had some fancy names but it was basically an x-ray shoe fitting machine. The person trying on shoes would stand on the little shelf and put their feet wearing the shoes they were trying on in the little slot at the bottom. You and your mom (dads never took kids to buy shoes in those days) and the shoe salesperson could look through the slots in the top and see how the shoes fit your feet.
I don't know how effective they were for shoe fitting but they sure were fun. I not only stuck my feet in one of those things everytime I got a new pair of shoes at our local Buster Brown shoe store, but my friends and I would stop in just to have a look at our feet within our shoes, probably telling the clerk our mom's wanted us to see if our shoes still fit.