The CV1698 is an amplifier tetrode with a μ of 4.6 mA/V and an unusual heater rating. It is a UK Post Office design known as the POVT148 or VT no. 48.
Our other CV1698 has the classic shouldered envelope whereas this has the glass tubular envelope and is thus most likely to be of later production.
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 dark coating inside the glass prevents seeing the inner structure.
The B7 base pins are brand new. Above the lower mica can just be seen the wire grid.
The glass blurs the inside but the grid can be seen.
The classic envelope is 31 mm in diameter, and excluding the B7 base pins is 102 mm tall.
References: Data-sheet. Type CV1698 was first introduced in 1946. See also1946 adverts.
