The E2635 is a development triode pentode from M-OV. Both heaters are connected in series and this suggests a series heater chain type of valve that would most commonly be found in television receivers.
The thin triode on the left is full height and the pentode is on the right. All three wire grids can be seen.
The holes in the top mica for the triode supports are empty. The pentode has copper supports for both inner grids but it is the screen grid that is fitted with a heat sink. The pentode is clearly for power output not voltage amplification.
The thin glass tube envelope is 21 mm in diameter, and excluding the B9A base pins is 64 mm tall.