This item is a vintage aviation Turn and Slip Indicator, specifically identified as an RC Allen unit. Function: It is a gyroscopic instrument used by pilots to measure the rate of turn and to coordinate turns, ensuring the aircraft is not slipping or skidding. Key Features: It features a "4 MIN TURN" display, indicating a standard rate turn takes four minutes for a full 360-degree rotation. Power: It operates on "D.C. ELECT." (Direct Current Electrical) power, typically found in various aircraft. Condition: Similar used units are sold as core items for parts or restored for aircraft refurbishment.