original c. 1925 "g series" diathermy device or machine enclosed in original walnut wood cabinet with a beveled edge clear glass top plate. the machine was manufactured by the h.g. fischer & co., inc., chicago, il. diathermy is a form of physical therapy in which deep heating of tissues is accomplished by the use of high-frequency electrical current. american engineer and inventor nikola tesla in 1891 first noted that heat resulted from irradiation of tissue with high-frequency alternating current (wavelengths somewhat longer than the longest radio waves) and pointed out its possible medical uses. k.f. nagelschmidt, a german physician, in 1909 coined the term diathermy, meaning heating through." the device powered a glass probe or "violet wand", which is used for the application of low current, high voltage (min 10kV to max 50kV typically), high-frequency electricity to the body using a tesla coil, originally sold as a supposed medical device claimed to be useful in electrotherapy, though, since the 1990s, it has been used by some into bdsm sex as a sexual stimulation device (i.e., vaginal probe) and by hairdressers to stimulate the scalp. measures 15 x 22 1/2 x 12 inches.