McVitie Weston valve collection, valve
Valve, marked 180, flat glass envelope about 2in diam x 1in thick overall, with convex window, end tube 0.5in diam x 0.75in long carrying open grid anode, with opposed evacuating pip, cathode contact pip at centre of flat side, (RMW/P13 - McVitie Weston number), by Unknown maker.