Inertial Reference Integrating Gyroscope from the Apollo program, 5″ in length and 2.75″ in diameter, with upper parts marked: "IRIG PREAMP ASSY, 2021785-011, ACSK H102" and "Electron Gyro Suspension Capacitor, 2021503-34 REV B, E52605, T.58.5," with tape to top annotated "10A21." Metal directional label to bottom stamped as "Unit No. 10A21." In very good to fine condition. Three IRIGs were mounted on the Apollo Command Module and Lunar Module IMU stable platform and sensed displacement in three dimensional space. The magnitude and direction of displacement were converted to output signals that drove gimbal torque motors to restore the stable platform back to its ‘nulled’ alignment.
