Direction Finding DF Indicator of R.1155 Nav-Com System
Here is a WWII-era Direction Finding (DF) Indicator as used in aircraft of the British Royal Air Force, such as bombers Avro Lancaster, Handley Page Halifax, and Vickers Wellington, and patrol bomber Short Sunderland.
The DF Indicator received its signal from the R.1155 receiver in the radio (wireless) compartment. By seeking a signal from a ground transmitter, the indicator displayed the direction of the transmitter in relation to the aircraft by moving the L and R pointers in toward the transmitter. Once both pointers are vertical, the aircraft is dead-on the position of the transmitter, often the home airfield. The indicator was typically installed on the front top of the main instrument panel, see photo of the Lancaster panel from its Pilots Notes showing the location of the indicator.
This example is in fair condition given its age. The glass dial shows some crackled interior coating. Measures 3.25 inches diameter and ~2 inches deep.