Here is an example of a WWII-era Remote Indicating Compass AN-5730-2 as appeared in the cockpits of many aircraft of the US Army Air Force and US Navy, such as bombers B-17, B-24, B-29, B-25, and fighters P-38 and P-51, according to the US Army Air Force's Interchangeability Guide dated Feb 1945. The indicator has a serial number prefix of "42" evidence of a year of manufacture of 1942. See spec sheet in the photo gallery. It was also used in the Gyro Flux Gate Compass System as a remote direction indicator.
The Remote Indicating Compass system is described in the Index of Aeronautical Instruments dated 1944 as follows:
"When a compass installation free from magnetic deviation is required, the remote indicating magnetic compass may be u.sed. It consists of:
a. Transmitter AN5730-3
b. Indicator AN5730-2A or AN5730-6'
c. Inverter Pioneer Part No. 12117-6-A
The transmitter containing the compass magnet and float can be operated in any part of the aircraft where local magnetic disturbances caused by engines, guns, turrets, ammunition, etc., are at a minimum. The reading is electrically transmitted to the indicators, which are mounted in a location convenient for reference. Indicators are not affected by local magnetic disturbances, and from one to three indicators may be operated from one transmitter. The remote indicating magnetic compass system can operate on any combination of frequency and voltage where the frequency is 13 to 17 times the voltage, i.e., 400 cycles, 26 volts; or 800 cycles, 52 volts.
An inverter is used for changing direct current from storage batteries to alternating current for operation of the system. In most cases, the same inverter which operates other electrical systems in the airplane may also be used for the compass.
The indicator face is usually installed in an upright position, and a pointer moves across it showing the direction of flight. A knob for setting a manually-controlled indicating pointer to the desired course is located in the lower left-hand corner of the instrument. When the settings of this pointer and those of the compass pointer coincide, the airplane is headed in the desired direction."
The Indicator is in good condition for its age. Measures 3.25 inches diameter and ~3 inches long.