c. 1838-40 Charles Spencer is making Horizontal Microscopes resembling the Microscope Achromatique Universel of Chevalier and also Goring's reflecting Engiscope. In 1847 he made a Chevalier type for Dr C.R. Gilman.

1843 Tolles Joins Spencer as an assistant

c. 1850 Spencer making Pritchard Type microscopes

1854 to 1865 Spencer forms Partnership with Eaton of Troy to form Spencer and Eaton-They advertised the Trunion Stand. The 1859 Catalog includes the Trunnion and Student stands. The Student stand was quite similar to the Student of Tolles
Tolles leaves Spencer about 1858

c 1858-1867 Tolles in Canastota

1865 Spencer & Eaton Breaks up and Clarence Spencer, O.T. May, John Green, Orlando Amos and C.X. Dalton go to Join TOlles in Canastota.

1867-1872 Tolles goes to Boston to become superintendent of the BOW organized by Charles Stodder and some businessmen.

1872 to 1883 Tolles Runs BOW without Stodder as it was not very profitable and Dalton stays as brass maker

November 1883-Tolles dies and Dalton takes over BOW until at least 1895. Although it is clear that Dalton made the stands both before and after this, it is unclear to this author if he ever made his own objectives after his limited stock of Tolles objectives ran out. Just like the BOW before, he was an agent for Zentmayer, and the famed optician Wales. It is likely that many of the objectives used with his later microscopes were by contemporaries like Wales or Herbert Spencer. In this way he was very much like Walter Bulloch who also made stands but not lenses.

1865-1875 Spencer and Sons Canastota. This included Herbert and Clarence

1875-1880 Spencer and Sons in Geneva associated with the Geneva Optical Works

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1880- H.R. Spencer & Co and HR sold Acme stands

1889 HR moved to Cleveland OH,

1890 HR moved back to NY but to Buffalo

1893-95 Joined with Fred Smith to form Spencer & Smith

1895 Spencer Lens Co formed

1935 America Optical, mainly a spectacles complany, acquires Spencer Lens Co