The 50C5 is an American audio output beam tetrode. It was designed for operation with anode voltages of 110 Volts and would be found in broadcast radio receivers with series heater chains.
Rather than dropper resistors in the cabinet the USA market tended to use 'line cord'. Line cord had resistance wire built into the mains cable. In use the cable became quite warm - disconcerting!
With an anode load of 2,500 Ohms it would deliver in a single ended configuration 1.9 Watts at 9 % distortion.
The oval anode seen from the end.
The two wire grids and flat cathode. The heater has twelve loops running through the cathode tube.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 58 mm tall.
