"Philadelphia Directories:  1867-1875 Kuebler & Seelhorst inst makers, William J. Kuebler, Frederick Seelhorst.  On October 1, 1867, Kuebler and Seelhorst were granted patent No. 69450 for a method of adjusting eyepieces and objective glasses in telescopes.  Gurley serviced a Kuebler & Seelhorst level from Dallas, Texas in 1887, and a 5" Engineers Transit from Frederick, Michigan in 1900."

"William J. Kuebler (1827 - 1900) - Philadelphia Directories:  He is listed from 1867 to 1900 as an instrument maker and optician.  He was born in Germany in 1827 and died in Philadelphia on August 17, 1900."

"Frederick Seelhorst (1813 - 1887) - was born in Italy in 1813 and died Philadelphia May 1, 1887.  Philadelphia Directories:  1867 to 1887 Seelhorst F. & J. instrument makers."  [The J. stood for Julius Seelhorst, born 1844 in Philadelphia and died there 1900.]

Reference:  Smart, Charles E.   The Makers Of Surveying Instruments In America Since 1700  Troy, New York:  Regal Art Press.  1962