The primary theorem of electrical calibration industry, this is based at the fact that the owner, he gains confidence when several Calibration Reports (over time) they are in agreement.
The undocumented use of Calibration Reports, this is using them as reference so to test your portable calibrator output.
Agilent / Keysight this does something worth mentioning over the years, they do deliver by default, a Calibration Report with any NEW of their HH DMM.
Due to this offering, even the uneducated owner, he can obtain knowledge, of the actual measuring performance of the specific measuring instrument.
For example at U1272A HH DMM.
At 30V range DC, 10V REF, the reading can be 10.000 or 9.999 or 10.001 ( all acceptable ).
While at 300mV range, 100mV REF, the acceptable readings these might be in the window of 15 counts.
In conclusion.
An good study of your calibration report, this can deliver significant knowledge and understating of how your DMM behaves.
You also becoming aware of upper and lower acceptable range of readings.
Calibration Reports they are valuable assets, that you should keep in storage as reference points.
The major problem with electrical calibration labs, since 2011 and up to date, the terms of cooperation with consumers, these are not that clear.
The cost of Calibration Report with detailed data, the shipping costs, the payment method, all these details they are not published, so us consumers to be able to select THE best priced service.