This paper was presented at the Twentieth National Conference of the Society of Aeronautical Weight Engineers at Akron, Ohio, May 15 – 18, 1961. When determining the mass of an object, highly precise weighing operations are of little consequence unless the validity of the standards comprising the basis for the values determined has been established. Moreover, since the working standards --- those actually used for calibrating a weighing scale, a testing machine, a force transducer, a test weight of equal or less precision, and the like --- probably will be several steps removed from the primary standards, each step in the derivation of any standard should be properly documented so that the genealogy of the working standard can be traced to the standard of the United States. Certificates and reports issued by the National Bureau of Standards are examples of good documentation.
In this country, the units of mass measurements, both metric and avoirdupois, are based on the platinum-iridium kilogram procured from the International Bureau of Weights and Measures and designated as The Standard of the United States of America. This particular standard is identified as Kilogram No. 20. Its mass, and the mass of each of the prototype kilograms of other nations signatory to the International Metric Treaty, is known; the uncertainty in every case being only a few hundredths of a milligram.
As custodian of this national standard, the National Bureau of Standards is charged with the responsibility for dissemination of other mass standards, properly derived from the National Prototype, as a means for the promotion and maintenance of uniformity of mass measurements throughout the nation and in agreement with the standards of other nations. It is the purpose of this paper to set forth briefly how the National Bureau of Standards discharges this responsibility.