The N37 is a television type audio output pentode.
The load impedance is 6000 Ω and the cathode resistor is 330 Ω. At 10% total harmonic distortion the valve can produce 2.3 Watts of audio.
The working face of the anode is flat. The suppressor grid support can be seen through the holes in the anode wall. Above the lower mica can be seen the wire grids. Both the control and screen grids are wound on copper supports.
The Osram paper label.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 60 mm tall.