Casella described this as a "Military or Target Telescope" that "will show the time by a clock at six miles distance, and the form of the
rocks of Calais from Dover, a distance of twenty-one miles." It has an
achromatic objective, and a tapered four-draw brass body covered with leather. Its four-element erecting eye piece is "pancratic," which means that it can produce various magnifications (in this case, of 20, 25, or 30 times). It was probably made after 1878 when the U.S. Coast Survey became the U.S. Coast & Geodetic Survey. It was transferred to the Smithsonian in 1929.
Louis Paschal Casella (1812–1897) was an Italian immigrant who opened a
shop in London in 1848, offering a wide range of meteorological, mathematical,
optical, and philosophical instruments, and photographic apparatus. Casella
prospered, and soon obtained appointments to the Prince of Wales and several
government agencies. With Charles Frederick Casella in charge, the firm became C.F. Casella in 1897, and C. F. Casella & Company Ltd. in 1910.
Ref: L. Casella, List with Notes of Standard Meteorological and Other Instruments for Observatories, Travellers and Explorers, and the Army and Navy (London, 187?), p. 61.
Gloria Clifton, Directory of British Scientific Instrument Makers
1550-1851 (London, 1995), pp. 51-52.