Paramagnetic oxygen analyzer.  Mechanism was a glass dumbbell suspended by a glass thread between the poles of a magnet.  The amount by which the dumbbell rotated depended on the amount of oxygen in the sample chamber.  A light reflected off a mirror attached to the dumbbell and showed up as a light spot on the front panel display. The black bulb in the rear was used to pull a gas sample into the analyzer. Photo is courtesy of Jim Sullivan, Supervisor, Pulmonary Diagnostic Laboratories at Memorial Sloan-Kettering Cancer Center.