"William Helffricht was born in Germany in 1807 and died November 17, 1876 in Philadelphia, Pennsylvania.  In the Philadelphia Business Directory of 1838 there is an advertisement "Wm. Helffricht has taken over the old establishment stand of the Wm. Davenport Sign of the Quadrant 25 South Front."  He is first listed in the Philadelphia directories, 1837, Helffricht, William, mathematical instrument maker 26 S. Front; 1848, Helffricht, William mathematical instrument maker 255 Front; 1876, Helffricht, William mathematical instrument maker 140 S. 6th."

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