The device in your image is the Dwyer Model UTG Ultrasonic Thickness Gauge. It uses high-frequency sound waves to measure the thickness of various materials, such as metal or plastic, from just one side.
DwyerOmega +3
Key Specifications
Measurement Range: 0.047 to 7.874 inches (1.2 to 200 mm).
Accuracy: ±0.5%.
Sound Velocity Range: 500 to 9000 m/s.
Power: Requires four 1.5V AAA batteries.
Materials: Suitable for steel, cast iron, aluminum, red copper, brass, zinc, quartz glass, polyethylene, PVC, and more.
DwyerOmega +2