Oil Quantity Indicator, US Navy P5M-2 Marlin
Here is a capacitance-type Oil Quantity Indicator for engine #2, 0-620 lbs, as appeared on the pilots aft control panel of the US Navy's patrol bomber / seaplane P5M-2 Marlin (see illustration showing the location on the panel from the P5M-2 flight manual dated 1956). Made by Minneapolis-Honeywell, part # JG7020A-36, it's data label says Fuel Quantity but its dial indicates Oil Quantity (likely the same design used for both fluids). Measures 2.25 inches diameter and ~5 inches deep.
It is in exceptional condition given its age. The glass and case are intact and dial markings are clear and precise.