The DW4/350 is the Mullard version of this standard directly heated full wave rectifier. The Mullard name and Type designation can just be seen on the right of the main image - it is very feint.
There is no minimum series resistance quoted and the maximum value of reservoir capacitor is given as 16 μF.
The filament tension springs above the top mica. The side panels bend and grip the shoulder of the envelope. The filament can be seen as an oxide coated ribbon in the hook of the tension spring.
The ridges in the anode give stability to the thin nickel sheet. The filament ribbon is welded to the supports and the filaments are run in series.
Here the front filament supports connect to the base pins, the rod at the back connects the two filaments together.
Top view. The right hand filament is in focus and the coating can be seen.
The classic envelope is 49 mm in diameter, and excluding the B4 base pins is 115 mm tall.
References: 1043 & 1040. Type DW4/350 was first introduced in 1936. See also1936 adverts.
