Mullard Transmitting Valve
Large transmitting valve made by Mullard in wooden crate. Glass - or possibly silica - valve with plaited copper wire at both top and bottom. The top of the valve is marked TYS5 3000 395.
Material include copper, tungsten and nickel, see note below, and possibly lead.
The TYS5-3000 was designed for both transmitter use and for industrial heating applications.
The TYS5-3000 is directly heated with a thoriated tungsten filament. The top of the grid cylinder is visible as is the grid spiral emerging from the left of the top ring. The outer cylinder is the nickel anode.
Information from 'virtual museum' The National Valve Museum http://www.r-type.org/static/mission.htm