Rens 1374d tube


Anyone have a slight idea about the Rens 1374d tube. This tube i have is a b4 socket, not the az1 series. Need to know what the side screws on the tube base is for. Any help would be great. Thanks!!
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very likely a pentode. screen connected at the side screw.
rens is a RundfunkEmpfängerröhre for Niederfrequenz mit Schirmgitter. I assume you can understand that amount of german ;)

cheers,

Anton