Koehler Brothers, 1890-10-31, 1893-07-27, 1901-09-12, Container: Letterheads of Saginaw Businesses - Box 1, Folder: Two. Business and Industry, COL-BUSINESS. Hoyt Library Archives. https://archive.saginawlibrary.org/repositories/2/archival_objects/11815 Accessed December 06, 2025.