McVitie Weston valve collection, MOV/GEC valve, type D.E.R.
MOV/GEC valve, type D.E.R., marked - Radio Section G.P.O., (RMW/Y144 - McVitie Weston number), by M-O Valve Co. Limited; General Electric Company Limited.
MOV/GEC valve, type D.E.R., marked - Radio Section G.P.O., (RMW/Y144 - McVitie Weston number), by M-O Valve Co. Limited; General Electric Company Limited.