It is a portable ambient temperature black body used for single point calibration verification and checking of Infrared Thermal Imaging Cameras and Point Infrared Thermometers.
To use this portable black body simply turn the instrument on and choose either °F or °C. Set your thermal imaging camera or IR thermometer to the correct emissivity. Aim at the target area and compare the readings. The result will confirm your infrared unit is within tolerance, and you can calculate the correction for zero error.