The EL35 is a larger more powerful audio pentode than the small receiver types and was intended for use in class AB. The EL37 25 Watt pentode was the replacement for the EL35.
The EL35 was used for audio amplifiers and modulators for small Amplitude Modulated transmitters. As a single ended audio stage the valve would deliver 6 Watts and in push pull a pair would form an amplifier capable of generating 21 Watts in class AB. The design dates to the early 1940's.
The image reveals that the EL35 uses a mesh anode.
This closer view shows the three grids and the large cathode tube. The control grid has copper supports and heat sink fins at the top.