We do not issue calibration certificates as our customer base covers too many use cases requiring a wide variety of calibration requirements, but you can certainly send our sensors to a calibration facility of your choice. There are many advertised online who can test at the levels you need and provide regulatory documentation such as NIST traceable certifications.
For example, one calibration services company is Essco Calibration (http://www.esscolab.com). It's not an inexpensive process (you will need to check prices with them), but they do both commercial calibration and the accredited calibration. Both are traceable to NIST and will include the as-found and as-left data on the calibration certificates.