!!Introduction
Obviously even were it desirable it would be impossible to collect together all historical objects of interest in the history of calculation. Certainly no such attempt has been made for this collection.  Rather what has been collected together is what appeals as aesthetically interesting as well as evocative of the broader story in which they play their part.  However, in the course of assembling an account of that broader story it is often necessary to refer to additional objects which are not represented in the collection.  This is a list of those objects where it seems helpful to provide useful external references and other information about them.

Since there are several excellent sites that provide the basic documentation there is no need whatsoever to reproduce that effort here. Particular use will be made of   [[http://www.rechenmaschinen-illustrated.com/|Rechenmaschinen-Illustrated]], [[http://home.vicnet.net.au/~wolff/calculators/|John Wolff's Web Museum Calculating Machines]], and [[http://www.rechnerlexikon.de/en/artikel/Main_Page|Rechnerlexicon]].