The CV1197 is a UHF oscillator triode and the prototype was the RL18. The old Admiralty service code is NR88. The Mullard commercial version is the EC53.
Here the insulated heater wires can be seen entering the cathode tube. The lower tips of the copper grid supports can be seen in the mica strip.
The triode section is 5 mm long and 1.5 mm thick and was hand assembled.
The thin glass tube envelope is 15 mm in diameter, and including the B3G base pins is 52 mm overall.
References: Data-sheet & 1043. Type CV1197 was first introduced in 1941. See also1941 adverts.
