The E1308 is an experimental or development valve from M-OV. The serial number on this exhibit is 39. The heater and cathode is at one end and a central wire electrode can be seen as well as a glass insulated electrode at the opposite end to the cathode. This arrangement strongly suggests a thyratron or gas filled triggered triode.
The Serial number and heater voltage. No other markings can be found.
The outer containing can is bright and connected to the cathode. The vertical wire close to the cathode would initiate an ionised discharge at a lower voltage that that required between the cathode and the distant anode rod.
A closer view of the lower mica and screening.
The insulated heater and tape connection to the side support and thus the screening can.
The screening at the top makes viewing the top connections difficult but the central electrode does have a top support.
The classic envelope is 44 mm in diameter, and excluding the B5 base pins is 102 mm tall.