The RV120/350 was designed to work with a maximum reservoir capacitor of 32 µF and to have an effective series resistance of 100 Ohms. The RV120/350S was the same valve but fitted with a Ct8 side contact base cap.
The side view showing the method anode construction. The sheet metal is folded to shape and notched locked at a supporting side flange that also aids heat dissipation and grips the fixing rod.
In addition to the paint markings on the valve, this image clearly shows that the filaments are thin inverted V ribbons in each of the anode cavities. Note the oxide coating on the bright ribbon. The filaments are connected in parallel.
The top mica holding the electrodes firmly in place in the envelope.
Looking down on the top mica the top of the filament can be seen with its supporting mica. The fixing of the anode sheet around the support rod is clear as is the thickness of anode sheet. The anodes are clearly complex pressings that have had to have been made in several steps.
The classic envelope is 45 mm in diameter and, excluding the B4 base pins, is 110 mm tall.
References: Data-sheet & 1043. Type RV120/350 was first introduced in 1938. See also1938 adverts.