This is a very nice tube tester. Transconductance is measured directly which is read on the old style Weston fan type meter. The 981 has a seperate 5KC oscillator for the grid signal, unlike Hickok testers which just utilize the 60Hz line signal voltage for the grid test signal. Has handy switch for testing dual section tubes such as 12AX7 without resetting main selector switches for each section. Nice quality toggle switches.
Leakage is measured on the meter rather than the less accurate neon type bulb.
Nice heavy duty gray hammertone metal carrrying case.