The "reference" EEC standard mass per storage volume is the EEC standard mass per storage volume as determined by measurement with a standard Community or national instrument constructed and used in accordance with Chapters I and II of
Annex I. ...The Community standard instrument shall be deposited with the Metrology Service of the Federal Republic of Germany. At least every ten years, national standard instruments shall, in conformity with Annex I, be checked against
the Community standard instrument and adjusted accordingly by means of a transportable standard instrument of the same type.
