[Boatanchors] Hickok 539 tube tester meter sensitivity

[HL1FB]

Hello;

     I am repairing a Hickok 539 series tube tester and I  need to know the internal resistance and sensitivity

of the large Mutual Conductance meter. I have manuals for 539 series but they do not contain the information.

The actual tube tester I am repairing is Hickok KS15560-L1 which I believe is very close to 539 series.

Could someone tell me about the meter?