The CV3886 (commercially the EF41) is a variable μ RF pentode for use as an RF or IF amplifier.
In the Mullard literature it is stated that although pins 3, 4 and 7 are internally connected together, it is recommended that the external cathode connection be made to pin 7 as this point offers the lowest connection inductance.
The main image shows the locating pip and skirt moulded into the main envelope. The connection between the soft glass envelope and the hard glass base shows the typical groove used by Philips.
The Philips identification.
Looking through the screening mesh the anode is a pair of strap joined plates and the grids are wire with the suppressor grid an open pitch helix.
A close view.
The thin glass tube envelope is 20 mm in diameter and, excluding the B8A base pins, is 52 mm tall.