Engine Gage Unit for US Army Air Force & Navy Fighters, 1944, AN-5773-1 C-130 The knob situated below the

The knob situated below the display rotates to oil reservoir 1 thru 4 (see photo of display partially rotated)

which would illuminate the inner rim of the dial when the knob is rotated

Here is a Rocket Station Distribution Box which appeared in WW2-era F4U Corsairs and TBM Avengers of the US Navy

Gyro Horizons

Engine Gage Unit for US Army Air Force & Navy Fighters, 1944, AN-5773-1 C-130 The knob situated below theThe AN 5773 1 Engine Gage Unit was used across a variety of aircraft of the US Army Air Force and US Navy during and after WWII. In particular, the AN 5773 1 made by Electric Autolite (aka Motometer) part number 10322 A was used in fighters P 38L Lightning and P 63 A & C Kingcobra according to the US Army Air Force's Maintenance Interchangeability Cross Reference Chart TO 00 45 1 dated Feb 1945. This example has a serial number prefix of AF 44,