E. G. Fischer and his colleagues in the Instrument Division of the United States Coast and Geodetic Survey designed this precise level in 1900. C. L. Berger & Sons began making levels of this sort around 1912, noting that they "follow absolutely" the Survey's specifications, "using 'invar' where specified, thus insuring a rigid maintenance of the adjustment of instrument under marked changes of temperature." This example dates from 1930, and belonged to the United States Coast and Geodetic Survey.
Ref: E. G. Fischer, "Description of Precise Levels Nos. 7 and 8," Report of the Director of the United States Coast and Geodetic Survey (1900), Appendix 6.
C. L. Berger & Sons, Inc., Catalog of Engineering, Surveying & Mining Instruments (Boston, 1927), pp. 43-44.
