The LD2 is a German transmitting triode from WWII. It was made by Telefunken and designed to operate in the high VHF - Low UHF region. The LD2 is a low power device probably used as an oscillator or early stage amplifier or frequency multiplier in a transmitter. The first letter L indicates that it was made for aircraft use.
Like most German valves of this period it was designed to have a Bakelite handle screwed into the metal part. The metal skirt has a key to guide the valve into the holder. Such an arrangement allowed rapid valve replacement while in service.
The Wehrmacht testing site BAL716.
More state ownership information.
The top with central threaded hole for the handle. SeeRV12P2000 for an example handle.
In this image the bright structure at the bottom is the grid support and shield. The black part is the anode. The heater connections are easily seen as is the coiled nature of the heater wire.
Here, on the left, the method of clamping the grid wires to the side support is seen.
Another view of the grid fixing. The Telefunken logo etched on the glass shows up well.
The hard solid base pins.
The wide glass tube envelope is 30 mm in diameter and, excluding the base pins, is 53 mm tall.
Reference: Data-sheet. Type LD2 was first introduced in 1943.