"William Stackpole was born in Ireland in 1819.  He died in Brooklyn, New York in 1895.  Robert Stackpole was born in Ireland in 1823 and died in Brooklyn in 1873.  Both William and Robert came to Baltimore, Maryland with their parents in 1833.   While there, William was apprenticed to a manufacturer of mechanical engineering instruments.  The Stackpole's settled in New York City in 1843.   New York city directories list:   William Stackpole, mathematical instruments, from 1843 to 1848.   In 1851 Robert Stackpole joined his brother William in business under the firm name of Stackpole and Brother (1851 to 1910)."

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