CLAROSTAT 1 MEG OHM POTENTIOMETER TEKTRONIX POT 311-039-00 2 WATT MADE IN USA
I have a B&K 747 tube tester. This is a mutual conductance tester. I also use a Tektronix curve tracer for testing triodes. I give a number of evaluations for tubes. The lines show how the tube conducts throughout that range.