The device is an automotive gauge, specifically an air/fuel ratio meter, manufactured by the Ideal Precision Meter Co.

Function: The meter is designed to measure and display several automotive parameters, including Amperes, Cylinder Output, and Air/Fuel Ratio.

Air/Fuel Ratio: The gauge's main purpose is to help optimize a vehicle's performance by providing accurate readings of the air and fuel mixture. The scale on the gauge has a "NORM" (Normal) range, indicating the ideal air/fuel ratio for efficient combustion.