The EL36 = 6CM5 is another
output pentode / tedrode developed by Philips. Characteristics between
EL12 and EL34. Not so much output power as an EL34, but maybe easier to
drive and less heat dissipation.
The successors as the EL500,
EL5000 or EL504 are optimized versions with cheaper bases / sockets in the
later versions (EL503).