[Hallicrafters] 5-pin socket pin-out / The plot thickens

[Waldo Magnuson]

Earlier I asked where pin # 1 is on a 5-pin socket.  I got seven 
responses.  Four of the seven stated that the isolated pin is pin # 3.  
The TV-7 tube tester schematic also shows the isolated pin is pin # 3.  
However a scan of the 1935 ARRL handbook  (thanks Chuck) shows the 
isolated pin is pin # 1.  Apparently there was a change in the standard 
after 1935.  However the set I am trying to get operating is a 1933 
Grebe with 1933 tubes and no pin numbering on the schematic.  The RCA 
Receiving Tube Manual for the tubes I am trying to test (24A and 27) is 
consistent with pin 3 being the isolated pin and pins 1 & 5 opposite 
being the filament.  Thanks all for the help.
73,  Skip  W7WGM