The CV437 is a high slope tetrode with a mutual conductance of 13.0 mA/V. The CV specification was issued by the GPO and they were used for telephone repeaters.
The prototype was the KT67. With the KT prefix this was a beam tetrode and the beam plates are visible.
The GEC paper label.
The B9G base.
The wide glass tube envelope is 40 mm in diameter, and excluding the B9G base pins is 81 mm tall.
