speed Camera Calibration

[Nelf]

Does anyone know how to get hold of a copy of a speed camera calibration certificate that does not relate to the time period when a speeding penalty occured? I recently received a fine and the camera was due for recalibration (annual service) two days later - presumably if changes had to be made, then my penalty would be based on inaccurate evidence? A small change in calibration would make a difference, due to the small difference between limit and actual speed.

Thanks in advance