B. H. Colby
circa 1900
Colby manufactured slide rules for surveying and engineering in St. Louis, Missouri around the turn of the twentieth century. The slide rules were sold by firms including Keuffel & Esser. See Bobby C. Feazel, "Colby's Slide Rule," Journal of the Oughtred Society 4, no. 2 (October 1995): 27-29 for information on two of his rules.