noun
prototype kilogram; international prototype of the kilogram
Refers specifically to the physical artifact that defined the kilogram until 2019; now primarily of historical and metrological interest.
キログラム原器はパリの国際度量衡局に保管されている。
The prototype kilogram is kept at the International Bureau of Weights and Measures in Paris.
2019年
Until 2019, the prototype kilogram was the standard for mass.