Meter Proving and Calibration Gage Western provides contract mobile proving services for PD and Coriolis liquid hydrocarbon meters in compliance with API MPMS Chapter 4.8. Our experienced team utilizes the latest in proving hardware and software and a comprehensive safety program to provide accurate, reliable, and safe proving and calibration of custody transfer and process flow meters. Gage Western also provides custody transfer meter proving witnessing services and will work with you to develop customized witnessing reports that meet your requirements. We currently provide services throughout Texas and New Mexico.