Please be informed that copies of calibration reports starting from year 2008 onward are still available in Sisgeo database ( FAQ#99 - Requesting a copy of calibration report ).
Older certificates are no longer available, neither in printed form.
In order to have an updated certificate, the instrument, if possible, shall be sent to Sisgeo for maintenance+calibration (FAQ#98 - How do I proceed to send Sisgeo instruments for repair/maintenance? How do I request an RMA? - UPDATED)