Ammeter 30-0-30 amps, Battery, Type D-30, US Navy PBM-5 Mariner
Here is an aircraft battery Ammeter, Weston model 606, type T-203, as appeared on the flight engineers panel of aircraft of the US Navy such as the patrol bomber / seaplane PBM-5 Mariner (see illustration showing the location on the panel from the PBM-5 flight manual dated 1944). The battery ammeter indicates the current flow through the battery charging system. A "zero center" ammeter, during charging, shows a (+) positive reading indicating the current is flowing to the battery (charge). A (-) negative reading indicates current flowing away from the battery (discharge). Measures 2.25 inches diameter and ~2 inches deep. On the face is marked "BU AERO" (Bureau of Aeronautics).
Item shipped may not be identical to item pictured here.