The CV1187 is a dual signal diode. The prototype was the D41 and the pre-CV code was the UK Navy NR66.
The KB/Z identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the Z identifies the maker as MO Valve Company, Hammersmith.
The construction is very different to the twin stacked diodes in CV1187, here the diodes are nested.
The coiled wire of the heater is inserted into the cathode as a single loop. The outer diode partly covers the inner one.
A closer view.
The balloon envelope is 41 mm in diameter, and excluding the B5 base pins is 75 mm tall.
