Micrometer type mechanical comparator
1855
1855
1883
1869 to 1897
1889
1889
1850-1857
circa 1876
1902
1835-1865
before 1889
1883
1850-1857
before 1889
1850-1857
1850-1857
earliest 1857
1835
1839
1850-1857
1871
1850-1857
1857
1846
earliest 1857
before 1889
1897
1871
1849
1850-1857
1833-57