The LG1 is a double signal diode. The working electrodes are mounted very close to the glass base and this was designed for deci-meter or UHF operation. The knob on the top of the envelope indicates that it was for use in sets that had easy change valves. These valves featured prominently in German equipment during WWII.
The BAL16 indicates the testing station that approved the valve for government service.
The RLM Eigentum lettering indicates that it was made for the Luftwaffe and probably used in aircraft sets.
The oxide coated cathode and small anode rings. On the left is a screen with the heater and cathode pins beyond.
A closer view.
The getter fires into the top of the valve.
The wide glass tube envelope is 25 mm in diameter and, excluding the base pins, is 53 mm tall.
Reference: Data-sheet. Type LG1 was first introduced in 1943.