The Mullard PCF86 is a miniature VHF TV frequency changer. It has been designed for the triode oscillator to supply 3.2 Volts peak to peak to the pentode mixer section.
This exhibit is an import and is marked as Foreign.
The support on the left is the g2 lead.
The oscillator triode is on the right. Note the screening under the lower mica.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 48 mm tall.
References: Data-sheet, 3002 & 1040. Type PCF86 was first introduced in 1960. See also1960 adverts.