The CV2134 is the UK government procurement code for the commercial 90CV caesium photo voltaic cell. It is sensitive to red and infra-red light.
The KB/OR identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the OR identifies the maker as Rank Cintel, Rotunda.
The cathode area as seen face on is 2.4 cm².
This image shows the semi-cylindrical photo-cathode.
Another example.
The side window envelope is 18 mm in diameter, and excluding the B7G base pins is 44 mm tall.
