As far as I'm aware, there is more than one Standard around for test instrument Calibration.
The majority of our test gear used by the Power Board here, is referenced to VDE Calibration standards.
But I'm not about to play the European card here.
I get my 16th ed meter and other test gear calibrated annually so I don't worry about the tolerance; it's all dealt with by the engineers
I can see how that would work, I do the same thing here, we have a VDE licenced lab in Wellington and I can send the gear up there on Monday and have it back by Wednesday morning.
Getting back to what Lyle said in the first place, 30% is a little hard to swallow though, considering that we have to have a stated accuracy of 0.5-1% accuracy with most of our test gear here.
30% with a Megger could give you some really wayward results!.