When the Office of Weights and Measures in the U.S. Coast and Geodetic Survey was transferred into the National Bureau of Standards (NBS) in 1901 it brought with it the internationally recognized Prototype Kilograms No. 20 and No. 4 to the new agency. These Prototype Kilograms are representative of the Kilogramme des Archives developed after the Treaty of the Meter was signed in 1875. The Kilogramme des Archives is held by the International Bureau of Weights and Measures in France. The Mass Standards Photographic Collection documents the kilograms and other mass standards held by NIST.
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