Fuel Quantity Indicator, Martin PBM-5 Mariner USN Patrol Bomber
Here is an original Fuel Quantity Indicator as used in the Martin PBM Mariner Patrol Bomber of the US Navy during and after WWII.
The indicator, Liquidometer PN EA41A-3 and Stock #R88-I-2044, displayed the remaining fuel quantity in each of 7 fuel tanks by turning the knob to the desired tank. When selecting the Forward, Center, Aft tanks, the display would flip the scale in the display window to the range of that tank. For the two bomb bay tanks and two wing tanks, the selector would first flip the display to that tank pair, and then would indicate left or right on that same scale by selecting left or right bomb bay or wing set.
This indicator was located at the station of the flight engineer. See the illustration of the flight engineer's panel from the PBM-5 Flight Manual dated 1944 with this indicator located lower center.
This example is in very good condition given its age. The knob turns and correctly changes the displayed fuel scale. There is a service label on the top from NAS (Naval Air Station) Norfolk (VA) with an overhaul date of 1-14-53.