The acorn valves were designed to have low capacitances and therefore work to higher frequencies than the normal valves. The 955 triode was introduced in 1934, and has a 6.3 Volt heater.
The force required to seat the horizontal pins into the spring clips of the base was quite enough to crack the envelope. Eventually a zero insertion force socket was developed.
The 955 was later re-issued on a B7G base as the 9002.
The original box is torn and battered but shows all the essential data. The Crown and AM of the Air Ministry, the VT121, RMA 955 Type designation and the old stores code of 110E/40. The box is 35 mm square and 56 mm long.
The small envelope with even smaller triode within.
The evacuation pip on the right and within the heater connections and on the left the black of the getter.
The acorn envelope is 14 mm in diameter and, including the base pins, is 32 mm tall.
