measurement standard recognized by signatories to an international agreement and intended to serve worldwide

EXAMPLE 1: The international prototype of the kilogram.
EXAMPLE 2: Chorionic gonadotrophin, World Health Organization (WHO) 4th international standard 1999, 75/589, 650 International Units per ampoule.
EXAMPLE 3: VSMOW2 (Vienna Standard Mean Ocean Water) distributed by the International Atomic Energy
Agency (IAEA) for differential stable isotope amount-of substance ratio measurements