Define calibration? Reason for question: Customer print says CAD data is master data for part size. Mylar check fixture is made from CAD data. Mylar is the nominal of the part perimeter with the upper and lower tolerance drawn. Lay the part on the Mylar and make sure the perimeter is in between the lines. Told mylars have to be calibrated annually. I have always understood calibration to mean adjustments can be made. No adjustments can be made to a mylar visual cheek sheet. It's replace when needed based on visually checking line quality. Verification is more what is needed and that is to make sure the mylar lines are still readable. Semantics, but verification is much quicker and less expensive than calibration. Verification would be visual check of revision and line quality on the mylar. Calibration is the measurement of each part characteristic on the mylar with another calibrated method (CMM - Calibrated steel rule, etc.). Input?