27th International Meeting of Collectors and Researchers
of Slide Rules and other Historic Computing Instruments

when & where   Due to the COVID pandemic the IM2021 cannot be held as a classical physical conference, but will be held as teleconference via the Internet on
september 11 & 12, 2021

We will use the Zoom system.

news   IM2021 is now history. We had a successful online conference with 90 registered participants, with a peak of about 80 present at a time.

This web site of the conference will stay online until mid 2022.

Unfortunately, I fell ill in september and also had some other problems, so I'm late with the final touches of the proceedings and with the editing of the videos. When they are ready, you will see a note here, and the participants will get an email.

Karl Kleine [2021-10-15]

theme / motto   This year's motto / theme will be

Computing Instruments Collecting in Pandemic Times

Presentations and discussions at IMs tend to be object centric. Participants are generally interested in details of specific slide rules / instruments, their scales, construction details, mathematical, technological or application background, and more the like. We certainly will have many of such contributions this time again; actually the majority of IM talks traditionally is of this nature. So, if you have a contribution of that kind, you are most welcome, and we urge you to submit a paper and give a talk!

But next to that we propose a session or two about the process of collecting and researching such items. There are many aspects to that, often of very practical nature, and many of these are generally not well documented. Many of these like cleaning, repairing, preserving, storing, documenting, catalogueing slide rules or other instruments are more or less independent of the current situation, except that we might have more time for these activities while we are at home in lockdown or even quarantine. Each of these activities deserves to be a subject of this IM; just two examples: (a) making really good photos of slide rules, which is harder than it seems at first glance, and (b) making and maintaining a proper inventory / catalogue of your collection.

Other aspects are heavily affected by the limits imposed on us by the pandemic, like the acquisition of items, as we do not have personal meetings, antique shops are closed, there are not live auctions, nor flee markets, nor boot or garage sales. Research became difficult, as libraries and archives are closed, and travel became restricted or even impossible. For these and other aspects we would like to have talks, papers and discussions about your experiences, both your happy moments before COVID-19 and now, using electronic communication like this teleconference. How much changed the Internet the collection of things like slide rules, (mechanical) calculators, and other mathematical instruments?

And then is one final issue, after collecting, the disposal of a collection. Degrading health with the inability to take care of a collection and ultimately death were always with us. A pandemic like COVID-19 significantly raised the probability of a sudden stop of our active life. Nearly all of the IM participants have private collections, not institutional ones where other people will take care of things in the future. So, what kind of arrangements have we made? What will happen to our collections? What are the items to preserve to posterity, what about the others? What about literature and often unique documents? What about electronic records on our computers and what about our web sites? It's not an easy subject, both with respect to practicality and even more so for our conscience. Nevertheless we should avoid avoiding the subject, COVID is here. Please contact the IM organizer and editor with your ideas on how we address the subject at the conference; he will be even more pleased to get some papers and presentations on this issue.

schedule and
  The conference schedule specifies the programme skeleton for our meeting. Due to the online form with participants from many parts of the world the schedule also addresses the issue of time zones.

The full conference programme with listing of all talks and times is available here.

You can also download a PDF version of the programme for printing.

auction   The Oughtred Society will auction 26 interesting slide rules from the estate of the late Conrad Shure in an online auction. A list of items and their description with photos as well as the auction procedures can be found on the auction web page.

registration   To participate in the meeting you have to register by email. The simple procedure is explained on the IM2021 registration web page, including a copy&paste form to provide the needed data for your actual registration.

proceedings   The conference proceedings will be published as a book in the same style and manner as IM2013 and IM2017. I tried hard to have them ready and in your hands in time for the conference, but circumstances and a couple of events delayed the completion, so that the book will be published after the conference.

Please check this web page on how to get your copy!

IM history   The International Meeting is a yearly event for collectors and researchers of slide rules and other mathematical instruments. The 2021 meeting will be the 27th in this series. The IM is traditionally organized by volunteers from the four national collector's associations, RST from Germany / German speaking countries, KRING from The Netherlands, UKSRC from the United Kingdom, and the Oughtred Society mainly from the USA (although the OS is an international society) on a rotational basis. The style of our meetings is informal and non-profit, in the best tradition of both amateurs in the classical sense and serious researchers.

More about the IM series of conferences is available on our IM history web page.

impressum   Organization, conference chair, proceedings editor: Prof. Karl Kleine (

Impressum and privacy statement