The 14R7 is a screened pentode and double diode. This is the classic valve design for AGC rectification, signal detection and first audio amplifier. The 14R7 pentode is of the semi variable-μ type and thus can also function for IF amplification.The 14R7 has a 12.6 Volt heater - suitable for vehicle battery supplies, whereas the 7R7 has a 6.3 Volt heater for AC mains equipment.
The Brimar logo and Made in England. The diodes sit below the pentode on the common cathode.
The wide glass tube envelope is 28 mm in diameter, and excluding the B8B base pins is 55 mm tall.
References: Data-sheet & 1040. Type 14R7 was first introduced in 1951.