Mayer & Wolf induction coil used for electro therapy. This was purchased  in a flea market in Zagreb and given to me by my son in law. It works but needs some further attention, I have cleaned the case and brass parts, removed the corrosion products from a long since dead battery and painted the insides of the two storage compartments. The output voltage can be controlled by sliding the iron core which has a brass knob in or out of the induction coil.The switch which is a more recent modification was open circuit and after taking it apart and giving it a good clean now works properly. The smaller compartment is equipped with two steel contact plates which were intended to mate with a battery and the switch was connected to one of these. I guess that this was a later modification and originally the instrument would have been used with an external battery connected to the two terminals marked E. Vienna probably 1890-1910
The two following pictures give an indication of the instrument as received.
Mayer & Wolf were instrument makers in Vienna, the firm started in 1850 and continued in business until 1945. They made a wide variety of instruments including items for electrical measurements and telegraphy.
Leads, wire brush and soft pad electrodes for applying voltages to different parts of the body.
Schematic of internal connections.
Electropathy (the treatment of disease by electricity) In the early days when electricity was a novelty people believed that it had curative powers but unlike other cures of the time electricity could be felt to be doing something. Electropathy which was very popular from 1850-1900, was said by 'quack' doctors and practitioners to cure almost anything, including mental illnesses. The patient held a metal electrode, while the 'healer' applied a second electrode to the ailing body part. Electrode attachments were manufactured in many shapes. The applied voltage was obtained (as in his instrument) from an induction coil powered from a battery or directly from a hand driven generator.