The International Meeting of Collectors and Researchers of Slide Rules and other Historic Computing Instruments or IM for short is a yearly convention of collectors and researchers interested in mathematical instruments, in particular those based on the laws of logarithms, especially slide rules. Although slide rules in their various forms are the main subject, we do cover the full range of mechanical computational aids. Most of these are analogue devices, for instance planimeters, but we also look at mechanical or even digital calculators.

IM participants come from all over the world, many of them on a regular basis. There are always a number of participants from Germany, the Netherlands and the United Kindom, but also from Switzerland, Spain, Finland, other European countries, Israel, the United States and even from Australia. Typically, about 40 to 50 people attend an International Meeting. Most of them are members of

  • RST (Rechenschiebersammlertreff, Germany),
  • KRING (Kring Historische Rekeninstrumenten, The Netherlands),
  • UKSRC (United Kingdom Slide Rule Circle, United Kingdom),
  • ARC (Amigos de las Reglas de Calculo, Spain), or the
  • Oughtred Society (USA / international),
and many of them are members of several of these societies.

In 2020 and 2021 the IM had to be held as an Internet based teleconference due to the COVID-19 pandemic. That changed much of the character of the conference, but it was also a chance to have a wider reach with more than double the usual number of participants.

IM history   After the end of slide rule production in the years 1975 to 1978 there was little interest in slide rules for the next decade. It was the boom time of the electronic pocket calculator, and then the start of the personal digital computer aera. In the early 1990s however, there was a revival of interest in slide rules, and collectors found each other and started informal meetings. Out of that grew the four of the five associations mentioned above, RST, KRING, UKSRC and the Oughtred Society, all founded in the 1990s. In recent years Hispanic collectors have also organized themselves in ARC.

But next to these local, then national come togethers, a regular European conference evolved. The informal style led to the name International Meeting of Slide Rule Collectors, as at the time of the first of IMs some of the national groups did not yet exist. That name essentially remained the same, though the areas of interest has widened over the years to include also other kinds of historical computing instruments. Furthermore, today we have not only collectors of these instruments as participants, but also researchers in the fields of the history of applied mathematics, science and technology. All that resulted in the somewhat heavy title of International Meeting of Collectors and Researchers of Slide Rules and Other Historical Computing Instruments, which usually is abbreviated to just IM, often followed by the year of the conference. The scope of interest has widened over the years, but "All about slide rules" still is the central theme.

Here is a list of all IMs with their places:

    1.  IM1995 — Utrecht (Netherlands)
    2.  IM1996 — Cambridge (United Kingdom)
    3.  IM1997 — Stein (Germany)
    4.  IM1998 — Hutwill (Switzerland)
    5.  IM1999 — Cambridge (United Kingdom)
    6.  IM2000 — Ede (Netherlands)
    7.  IM2001 — München (Germany)
    8.  IM2002 — Leamington Spa (United Kingdom)
    9.  IM2003 — Amsterdam / Breukelen (Netherlands)
    10.  IM2004 — Bad Driburg (Germany)
    11.  IM2005 — near Cambridge (United Kingdom)
    12.  IM2006 — Greifswald (Germany)
    13.  IM2007 — Lelystad / Enkhuizen (Netherlands)
    14.  IM2008 — Leamington Spa (United Kingdom)
    15.  IM2009 — Greifswald (Germany)
    16.  IM2010 — Leiden (Netherlands)
    17.  IM2011 — Cambridge, MA / Boston (USA)
    18.  IM2012 — Bletchley Park (United Kingdom)
    19.  IM2013 — Berlin (Germany)
    20.  IM2014 — Delft (Netherlands)
    21.  IM2015 — San Francisco Bay Area (USA)
    22.  IM2016 — Trento (Italy)
    23.  IM2017 — Bonn (Germany)
    24.  IM2018 — Stratford upon Avon (United Kingdom)
    25.  IM2019 — Scheveningen / De Hague (Netherlands)
    26.  IM2020 — online teleconference via Internet
    27.  IM2021 — online teleconference via Internet

The planning and the organization originally lied in the hands of a couple of volunteers of the original three associations RST, KRING and UKSRC. In the last decade they were joined by some american members of the Oughted Society. There is no formal IM organization, everything is based on informal contacts and gentlemens' agreements among those volunteers. Part of the agreement is also the date of sometime in september of each year, the informal style of the meeting, as well as the list of programme elements and their schedule, not ony for participants but also for their partners.

IM present   The COVID-19 pandemic changed the character of these yearly meetings, as it was not possible to meet in person. In place of a planned meeting in the USA in 2020 the Oughtred Society pioneered a teleconference via the Internet. When it became obvious that 2021 the circmstances made it impossible to resume the usual scheme with a meeting in Florence, Italy, and furthermore Italian collectors were unable to provide an online alternative, the convenor of the German RST, Prof. Karl Kleine, took the initative and stepped in as organizer for this year's International Meeting, IM2021, again as an Internet teleconference.
IM future   There is hope that the incredibly fast development of new vaccines for COVID-19 and its variants as well as general vaccination of the population will make it possible to have again regular conferences in 2022 in the USA (planned: MIT in Cambridge, MA) and Germany in 2023.