Mass. Gen. Laws ch. 164 § 103
The department, in accordance with its rules and regulations, shall make the inspections of gas required by section one hundred and nine and inspect, examine, ascertain and prove the accuracy of all meters which are to be used for measuring illuminating gas and which are to be furnished to, or for the use of, any consumer or company, and shall seal, stamp or mark every such meter, if it be found correct, with some suitable device to be determined by the department and recorded in the office of the state secretary, provided however, that for all such meters purchased or acquired by a gas company after the first of January, nineteen hundred and eighty-one, the department in lieu of performing the foregoing inspection, examination, ascertainment and proof on each meter, may perform said procedure on a sample of such meters as are to be inspected, examined, ascertained and proved according either to an attributes or a variables sampling plan, such as Military Standard 105D or Military Standard 414 promulgated by the United States Department of Defense, or such other sampling procedure as the department in its discretion may determine. A meter shall not be correct if it varies more than two per cent from the standard measure. The department shall keep a correct record of all meters examined by its employees with their proof at the time of inspection, which shall be open at all times for examination by the officers of any gas company in the commonwealth.
Mass. Gen. Laws ch. 164, § 103