Hello, Jimbo! Welcome to the Cove!
First, why do you require calibration? Did someone tell you it had to be calibrated? Has it ever been calibrated before?
In general, calibration is verifying an instrument/tool/other (unknown accuracy) against a N.I.S.T. tracable standard (known accuracy). So, for a calibration, this device should be checked against a calibrated standard of better accuracy.
I'm having a hard time visualizing the fixture, so bear with me. Is this a two dimensional tool, or a 3-D device of some type that the instrument fits into? Or is it some type of electrical fixture?
As far as calibration, what you would be verifying? Would you measure a distance, a hole diameter, or some level of volts/resistance?
You say there are several criteria verified against the datum. have you quantified these criterion and the acceptable tolerance? If this is dimensional, you might need a drawing for the facility to perform the calibration.
Sorry for all the questions. But, hopefully you got some idea of what calibration is. Please repost with a little more information when you can, so we can provide the best advise possible.