The MS4B glass version was issued before the catkin version MS4B that was issued in 1933/4. Later production was again in a glass envelope but with the classic shouldered shape rather than the earlier balloon. The original MS4 dates to 1929.
It is a tetrode from the early mains valve era with its 4 Volt heater and it offered 'maximum amplification', whereas the earlier MS4 was a general purpose screened grid valve. The screened tetrodes and pentodes were employed for RF and IF amplification.
The Osram paper label.
Internally the screen grid is, like the original SG valves, is made in the form of a mesh cage. The anode consits of two plates placed either side of the central core.
The classic envelope is 44 mm in diameter and, excluding the B5 base pins, is 121 mm tall.
References: Datasheet & 1040. Type MS4B was first introduced in 1931.