The German manufacturer Koch, Huxhold and Hanneman (KHH) sold slide rules under the company name, but were better known for their products sold by other retailers. In particular, the earliest slide rules sold by the Frederick Post Company were made by KHH before they started having slide rules made by Hemmi in Japan. They also made rules sold by A. Leitz in the USA, the Wichmann and Reiss companies in Germany, and by Hughes Owens in Canada, to name only a few.
KHH was formed in Hamburg, Germany in 1909 by three former Dennert & Pape employees, William Albert Klaus Diederich Koch, a carpenter in Hamburg, John Carl Rudolf Huxhold, a carpenter in Hamburg, and Carl Fritz Emil Hannemann, a mechanic in Hamburg. Making wooden slide rules covered with celluloid, as well as rulers and measuring sticks, their output peaked between World Wars I and II. William Koch died in mid-1930 and his shares in the company went to his son Wilhelm Arnold Chrisitan Koch. Slide rule production ceased in 1942 following the annihilation of its manufacturing plant during an RAF bombing raid over Hamburg, which occurred one day after the death of John Huxhold. The company name was officially changed to “Huxhold and Hanneman, Hansestadt Hamburg” in 1943, though the company was formally folded in late August of 1944.12
Total number of KHH slide rules in the collection: 3. \(~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\)
|Pocket Rule||1919||L||wd||5||yes||5-in pocket rule; on back: C.E. Brignell, Coblence, Germany, Sept. 1919; Albert Martz company mark in well; special thanks to Andreas Fassbender for helping to identify this long-standing noID rule|
|Mannheim Multiphase Adjustable||1924||L||wd||10||yes||Post 1452; very early version; maker Koch, Huxhold & Hannemann; Made in Germany in well; leather case, stamped Posts Multiphase Slide Rule; L scale right to left; Slide Rule Data Slips on back|
|Mannheim Multiphase Adjustable||
||1925-1930||L||wd||10||yes||Post 1452; maker Koch, Huxhold & Hannemann; Frederick Post Co. Chicago // Germany in well; fine leather case, stamped Posts Multiphase Slide Rule; owner M.J.T.; L scale right to left; Table of Constants The Frederick Post Company on back|
Sources: Otto E. van Poelje, “Book Review: Koch, Huxhold & Hannemann”, Jour. Oughtred Soc. 21.1 p.41 (2012); online article by Georg Schreiber, found at https://www.rechenschieber.org/2003/04/wer-waren-koch-huxhold-hannemann/, and its subject text by Georg Schreiber, Koch, Huxhold & Hannemann Der Unbekannte Rechenstabhersteller aus Hamburg, Private Publication by Georg Schreiber, Tönisvorst Germany (2011). Many thanks to Andreas Faßbender for German translation and for many valuable insights.↩︎