I had something like this - seen on an old auction - when I was a teenager, a strange electric ray machine for easing rheumatism and the like. I didn't own it for medical reasons, it was simply my magpie soul that made me buy it from a junk shop on one of my regular trips into darkest Preston looking for kukris and wakizashis.
I have no idea if the science behind these period ray units was sound or whether these were plug-in quackery. I don't recall plugging mine in and sadly it vanished into the currents of time and space around 1980 when I moved out.
Did you have anything like this? I wonder if any where ever made for Victorian or Edwardian kids to play with?