Wilhelm (1840 - 1925) and Heinrich (1842 - 1907) Seibert began and trained alongside Ernst Gundlach and Edmund Hartnack in Germany in the second half of the 19th century. From 1867 to 1872 they worked as employees of the former until this year, and in collaboration with Georg Krafft, they bought the business from him after accumulating large debts due to mismanagement and emigrating to the USA. They manufactured a very good model of oil immersion objective which was very successful. After Heinrich's death, and after years of collaboration with Leitz, the company passed into their hands. By 1900 they had manufactured approximately 10,000 units.
References: "Billings Microscope Collection" pag 79, fig. 148
G. Turner, "Great Age of the Microscope", pag 315, Num catálogo 394
H. Moe, "The Story of the Microscopes", pag 215-220