This precision equal-arm, two-pan balance, constructed about 1901 by A. Rueprecht & Sohn of Vienna, was purchased by NBS in 1945 from the Case School of Applied Science. It was used for calibrating secondary kilogram standards against National Prototype No. 20 until about 1960. The whole instrument is encased in glass to lessen the effects of temperature and humidity changes on the buoyancy of air and to keep air currents from affecting the performance of the balance. All operations can be accomplished from a distance by a long control rod.
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