The following quote is taken from The Makers of Surveying Instruments in American Since 1700 by Charles E. Smart, 1962:

JOHN C. SACK (1823 -       )

San Francisco, California

He is first listed in 1858 directory, no occupation, same address as Thomas Tennett, Battery Street. From 1861 thru 1888 he is listed as an instrument maker with Thomas Tennett, Battery Street. From 1889 thru 1895 he is apparently by himself at #4 California Room 7. In 1895 his residence is given as 540-1/2 - 15th.

He is not listed in the 1896 directory. The Federal Census of 1880 lists him as being 57 years old and born in Germany.