Dutch Circle of Slide Rule Collectors

Founded in 1991, The Dutch Circle (KRING) has grown into an informal group of about 60 collectors, sharing the following goals:

  1. mutual support of members for collecting and research
  2. promotion of public knowledge and awareness of the historical interest of the slide rule

These goals are pursued by issuing our periodical "MIR", by organising meetings, presence at fairs, by publishing papers, books, catalogues, interviews and by communicating with Dutch and international  communities of collectors and other interested parties.

End 2004 the area of interest has been expanded, and the name of the Circle was changed to:

Kring Historische Rekeninstrumenten   (Dutch Circle for Historical Calculating Instruments)

Breaking news...

slidechart IM2024 as a virtual ZOOM meeting
Date: 21 and 22 September 2024.
Time: about 9AM–1PM PDT, 12–4PM EDT, 5PM–9PM BST, and 6PM–10 PM CEST, so the presentations can be joined all over the world.
Theme: Slide Rules and Slide Charts for Special Subjects
Contact: @
More info: Announcement
New page: Help us identifying mysterious calculating instruments!
Articles from the MIR and books from the KRING 25th anniversary DVD are now avaliable online.

Announcing a new Book for Slide Rule Collectors:


… featuring for the first time all 52 currently known solid calculating discs and slide rules, plus the over a hundred slide charts, that were produced by the Dutch firm “ALRO” in the city of The Hague, from the mid-1930’s until the late 1990’s.

We proudly announce “THE ALRO CATALOGUE” (2020), in a hardback bound book format, with more than 200 pages of descriptions, tabular data, documentary annexes, a new coding system for identification, and most importantly the high-resolution colour images of each and every ALRO that is known today.

“THE ALRO CATALOGUE” is for sale at € 35.- + shipping costs
For more information - and ordering - click here

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