International Workshop BP

Chris' mystery circular slide rule

Denso.

Click images for magnification

Front Back

Data:

  • This is a standard circular Slide Rule with scales with not-standard name codes.
  • DENSO is a worldwide operating industry related Japanese company. But no information about a DENSO Slide Rule is available.
  • It looks similar to the “ALRO Small” slide rule, but without a name or number.
  • Another similar item is “ALRO Den Haag” and “ALRO HAAKSBERGEN” or “ALRO Ericsson”, but not the “ALRO Lettergieterij” (has no scale indicator N), with advertisement
ALRO is famous for the production of about 30 different types of metal box circular Slide Rules. ALRO also produced many Slide Charts without its name on it. Often Slide Charts have no producer name, but with the help of the (retired) ALRO owner it was possible to publish a catalogue book with photo's of nearly all 100 plus Slide Charts of different shapes. There are not many books with a complete overview of all produced Slide Rules and slide Charts of a single manufacturer. The “ALRO Catalogue” can be ordered through the KRING.
  • See Otto van Poelje's “ALRO Catalogue” Item AC-1.45a (no advertisement) & AC-1.45b (with advertisement) are exactly the same in dimensions and scales.
  • Front side: N² used for A and N used for C on the yellow disk
  • The front side has a white inner disk, which can turn within the yellow outer disk by using the “screw”. The plastic cover has a line as cursor and can move independently.
  • Rear side has the scales N used for C, N³ used for K, TG and SIN
  • The rear side has only fixed scales and no correlation with the front side. The plastic cover with line as cursor is coupled to the “screw”.
  • Diameter disk 6 cm, very small.
  • Black plastic cover ring.

Questions:

  1. https://logos-world.net/denso-logo/ The style of writing the name is different than the (Japanese) DENSO Corporation logo.
     
  2. Is this an ALRO Slide Rule?
  3. Is the famous DENSO tape produced by the DENSO company?
    DENSO tape 1952 DENSO tape is made by Winn & Coales (Denso) Ltd in the UK, which has no relation with the Japanese DENSO Corporation.
    The logo on the slide rule looks like the logo used on DENSO tape in the late 1940's, 1950's and 1960's. Andries de Man
     
  4. What can be said about using other code for scales.
     
  5. Who knows if and when codes switched to the common A, B, C, D, etc.
     
  6. Which companies used other codes for scales?