On Offer here is this early 20th. A precursor to the modern oscilloscope, an apparatus built in the early 1900s for the visual study of alternating current characteristics.In operation, the cathode is covered for part of its length with a blue glow, the coverage depending on the applied voltage. The distance that the glow extends along the electrode is a function of the instantaneous value of the potential of the electrode. When an alternating potential difference of 750 to 1500 volts is used, and the electrodes are viewed in a rotating mirror, the potential wave form is clearly seen.
No cracks the Tube is good. Probably In a school or college scientific lab. At the time of listing.