If the flat ones, are just round ones seen in Side Elevation only, then . . . .
~By touching it the spark should join the area that you are touching.
~Avoid touching ANY metal to it! The metal will heat-up by induced charge build-up!
~I'm fairly sure that you could destroy the files (& formatting) on a floppy disk by holding it close to (or against) the surface of the device!
~ Don't know how these devices are as to production of E.M. Fields or Radiation?
I've owned a spherical version for 8 years (or more).
You get a freaky display by touching your open mouth to it, and watching this with a mirror!!
When touching the device; you build a charge that you can discharge to another person via the finger-tip on your other hand!!