Antenna, Mast VHF Type AN-104-AX HH-3 Helicopter likely used by the US

likely used by the US military during the 1940-50s: Voltmeter DC 30-0-30 Volts

25 inches diameter and 6 inches deep

The right knob cages the gyro when pulled

It was also used in versions of US Army Air Force WWII fighters P-38

and the unit is 14 inches high

Antenna, Mast VHF Type AN-104-AX HH-3 Helicopter likely used by the USThe AN 104 is designed for 100 to 156 MHz, and also contains an anchoring hole for an HF wire antenna support. It thus serves as the VHF antenna and the forward support for an HF antenna. the AN 104 series is the most common US VHF aircraft mast of WWII, and can be seen behind the cockpit of many allied fighters and mid spine on multi engine aircraft, with an antenna wire connect from the top of mast to the top of the tail. According to VHF AN ARC 5