The Type 35 is a variable-μ RF tetrode, it is believed that the 35E is a variant of this. The 2.5 Volt heater was the standard for American AC valves until the 6.3 Volt standard emerged in the mid 1930's.
The construction looks much the same as the 51, which is equivalent to the Type 35.
The outer screen. On the glass is the Type 35E.
The base pins.
Thanks to Mark Mallison for sending the images.
The classic envelope is mm in diameter and, excluding the UY base pins, is mm tall.
Reference: Type 35 datasheet. Type 35E was first introduced in 1931.