NOS GE 12SN7 GTA TUBE short bottle side halo getter, copper grid support posts

Tested on a Hickok 539B tube tester for mutual conductance

Date code: 57-09 = 9th week of 1957

2600/2650 uM micromohos 

1640 uM micromhos mutual conductance per section is the minimum acceptable Gm value per section.

Please note the 539B tube tester is analog, so the test values may differ slightly from tester to tester.

Values are added as a means to show the tubes indeed tests as new, not an exact science. Your results can/may vary.