The Triotron WD2 is a battery triode designed for resistance/capacitance coupling. The earlier valves were normally transformer coupled due to poor amplification.The top set of parameters date to the introduction in 1927 and the lower set are the improved version that originated in 1933. The label on the base shows a measured mutual conductance of 1.0 mA/V indicating that this comes from the 1933 design.
The dome harries the etched identification. Clearly this was made in Austria.
The triode is mounted horizontally within the upper part of the envelope.
The balloon envelope is 41 mm in diameter and, excluding the B4 base pins, is 74 mm tall.
Reference: 1043. Type WD2 was first introduced in 1927.