Keuffel & Esser produced slide rules and imported planimeters for over 100 years. This web site is provided to help slide rule and planimeter collectors understand the works of this great American manufacturing company. It tells the story of a company and industry that evolved over five generations.

Clark McCoy and Michael O'Leary collaborated for many months to produce the scans for this site. Many collectors provided source copies of the K&E catalog slide rule pages to Michael for scanning. Clark and Michael scanned their own catalogs and added them to the scans from other collectors to build this comprehensive set of resources. Clark took on the daunting task of writing (and rewriting) the htmls that links all the scans together.

This project was started in 2002 and still is a work in progress. It started with a 50 Mb site hosted by Gary Lazarus. Within a year it was moved to a commercial server where today it is almost 900 Mb with about 2 Gb of traffic each month.

Today most of the catalogs scans are from the collection of Clark McCoy as are the pictures of most of the specimens. The purpose of the pictures of specimens is to document as much as possible the actual slide rules which sometimes tells a more expanded story than the catalogs. The variations in production with time is not always captured in the catalogs.

There are other K&E catalogs which, to date, are not yet available. To make this story complete we need many more contributions to the effort. If anyone would like to contribute other issues or have comments about these pages contact: email address

Tributes to slide rule friends that have passed on:


This site is dedicated to the memory of Michael O'Leary.

Web hosting is being provided by Clark McCoy. Many thanks to Gary Lazarus for hosting the original version of this site.

Scanning of catalog pages was originally provided by Michael O'Leary, Bob Otnes, and Clark McCoy.

The production of these web pages is by Clark McCoy.

Last And Not The Least: My favorite picture from the K&E catalogs: