Aircraft Instruments Technical Instructions, Air Corps Technical School, 1939
Here is a pre-WWII-era Technical Instruction reference manual for students of the Air Corps Technical School, published in October 1939, for use in training aircraft instrument technicians of the US Army Air Corps.
This 258-page, 8.5 by 11 inch technical manual covers all of the most commonly used instruments used in aircraft of the era, including pressure, temperature, and quantity gauges, compasses, turn, climb, and airspeed indicators, gyro horizons, and automatic pilots. For each, the manual describes the instrument's use, operation, installation, and service/inspection.
The manual is experienced but is in reasonable condition given its age.