The 2D13C is an indirectly heated double diode for radio receivers from the mid 1930's. Diode one is for AGC rectification and diode two is for signal demodulation. The 200 mA heater requirement is for use in a heather chain across the mains supply in universal AC or DC sets.
The separate double diode in superhet broadcast receivers was made obsolete by the introduction of the double diode triode in the mid 1930's.
See also2D13 and 2D13A for the Ct5 based versions also 2D13C for the metalised version.
The side view showing the pinch and cylinder.
The screen cylinder and the two rod anodes. The cathode is strapped to the cylinder. The second inner rod on the left has no visible connection. The matching inner rod on the right appears below the bottom mica.
The lower electrodes.
The close-up view into the outer cylinder. The multiple heater strands are easy to see.
The classic envelope is 38 mm in diameter, and excluding the B5 base pins is 90 mm tall.
References: Datasheet, 1040 & 1043. Type 2D13C was first introduced in 1935.