"Wm. Würdemann, Washington, D.C. No 163"
height 13 inches; horizontal circle 6 inches diameter; vertical circle 2.5 inches diameter; needle 4 inches; telescope 11 inches long
William Würdemann made this instrument during the period 1849-1881, and the U.S. Coast & Geodetic Survey transferred it to the Smithsonian in 1959. The horizontal circle is silvered, graduated to single minutes, and read by opposite verniers with magnifiers to single seconds. The vertical circle is silvered, and read by single vernier and magnifier.