This exhibit is a double signal diode on a Ct5 base. The top cap is required for the second anode. Later the 2D13A was introduced with the metalising connected to the cathode so that no top cap was required. The 2D13C, electrically equivalent, has a B5 base cap.
Part of the metal screening paint has come away revealing the two diodes stacked vertically.
The top diode showing the woven wire mesh anode.
The balloon envelope is 29 mm in diameter and, excluding the Ct5 base pins, is 84 mm tall.
References: Data-sheet & 3002. Type 2D13 was first introduced in 1934.