The DW4/350 is the Mullard version of this standard rectifier. There is no minimum series resistance quoted and the maximum value of reservoir capacitor is given as 16 μF.
The twin anodes are ribbed for strength and carbonised for efficient heat radiation.
The coated filament is a ribbon as can be seen clearly on the right of this image.
The top mica: the filament tension springs can be seen attached to a pair of central supports. Electrically the filaments are connected in series and so independent top filament support are required.
The classic envelope is 49 mm in diameter, and excluding the B4 base pins is 116 mm tall.
References: 1043 & 1040. Type DW4/350 was first introduced in 1936. See also1936 adverts.