The Marconi (MWT = Marconi Wireless Telegraphy) N77 is a miniature audio output pentode. In single ended configuration it will produce 1.4 Watts, suitable for a small broadcast receiver.
If used in push pull an output of 4 Watts is possible, but this valve was not expected to be used for hi-fi and for a radiogram there would be sufficient space to specify a physically larger valve. Output valves in the B7G base format ran very hot and not ideal if space existed for a larger envelope.
The MWT paper brand label. The valve will have been made by M-OV.
