McVitie Weston valve collection, valve, type 231A (Exptl)
Valve, type 231A (Exptl), cylindrical tube 2.5 in diam x 14.5 in long with longitudinal evacuating pip, two-ended with 5 flying leads at one end and 10 at the other, (RMW/Y398 - McVitie Weston number), by Unknown maker.