Advanced Instruments GPR-1500 GB ppm O2 transmitter with GPR 12-333 ppm O2 Sensor.It is used. It was either used once to be calibrated, or last used to successfully calibrate another device. Either way, the last time it was used, it was working correctly. I'm not sure how long ago that was and I have no way to currently test it.
The item in the pictures is what you will receive.
