FW4/500 Mullard GEC brown base black plate U18/20 full wave rectifiers

Description

Mullard FW4/500 audio rectifiers, full wave rectifiers with black plate and square getter.

They look the same as a U52 bu these have 4-pin base.

Equivalent of U18/20.

Z code on glass made at Hammersmith, London in the 1955.

All four valves have been tested and in full working order 100% emission.