Radio Transmitter BC-459-A, of US Army Air Force & Navy SCR-274N, AN/ARC-5 Command Sets B-57 and displays the direction on

and displays the direction on a vertically-mounted compass card

see photo from its flight manual dated 1944 showing the indicator

all for the elimination of errors caused by magnetism

We've been told that this was used in a version of the F4F Wildcat fighter

Radio Transmitter BC-459-A, of US Army Air Force & Navy SCR-274N, AN/ARC-5 Command Sets B-57 and displays the direction onThe BC 459 A Radio Transmitter was part of the WWII era US Army Air Force's SCR 274N "Command Set" (also used in the US Navy's ATA ARA and the later AN ARC 5 communication system where it was designated T 22 ARC 5). Frequency range is 7 9. 1 MHz. According to the Airborne Radio Equipment Manual of the Signal Section Air Service Command Dated April 1943, the SCR 274N was used in bombers B 17, B 24, B 25, B 26, and A 20, fighters P 38, P 39, P 40, and P