ARISTO-electronic pocket calculators from the collection of Prof. Dr. Jörn Lütjens.
Displayed are all  model versions of electronic calculators ever built by ARISTO.

This site is a part of the Online-Museum


Pocket Calculators

made by Dennert & Pape
Hamburg (Germany)

When in the 1970ies the slide rule era was ending, at the same time the spread of electronic pocket calculators increased rapidly. The famous slide rule manufacturer Dennert & Pape tried to compete on the market with a new product line.  From 1972 until  1978  they  developed approximately 20 different types of  pocket calculators. Almost simliar to their slide rules for schools the company followed the same product policy with a range from simple basic calculation to scientific applications.


Two competing concepts:
mini-calculator or slide rule?

The small but continuously growing 
group of pocket calculators was 
coexisting then with the still produced 
slide rules and had to gain parts on the 
market. In advertisements this doubling 
was used for argumentation 

("With ARISTO so or so")

The new slim design had the dimensions 62x151x18 mm. The calculators were quite slim at that time, because they fit into a jacket-pocket. They needed 3 AA-cells of 1.5V and the total weight was approx. 195 grams. Optionally run on main-power-supply and accumulators were possible. The display of the first generation was made by red LED’s, composed by blocks of 3. Every ARISTO electronic calculator had a smoky-transparent plastic cover, protecting the unit and being placed on the calculator bottom during use. Additionally a black case made of nappa-leather could be supplied.


The new design was an eye-catcher, making it a real great success for ARISTO. Beside of the clear form and color-design the nice feeling of the keyboard was remarked. On this example one could see realized a successful syntheses of form and function – one of the most important basic rules of a modern industrial design. This design applied a standard to the development of more types of calculator shortly after. With the same appearance, form and size followed in the years 1974 and 1975 the models M 75, M 36, M 65 and M 80. On the Hannover-Fairs the design won several times the award “Excellent Industrial Form”.

Here is shown the full spectrum of ARISTO electronic calculators. All items belong to my collection. The only exception is the picture from the demonstration calculators (these both items belong to the successor company of ARISTO). But take in mind that some models are issued in different, improved versions.

Click on the index fotos and you'll see
magnified images with some additional technical datas.


 This is the first in Germany in series
produced electronic pocket calculator: 

M 27

market introduction in fall 1972, 


These 6 calculators belong to the first generation of in-house developments.
The displayed calculators are here put in the order to their code numbers
but this doesn't correspond to their date of issue.

M 64 was the first by ARISTO entirely developed calculator.


M 36
(2 versions)
M 64
(2 versions)
M 75
M 75 E
M 75 ES
M 80
M 80 S

The second generation of calculators with enlarged keyboard:


M 42
M 42 S
M 66 S
M 76
M 76 S
M 85
M 85 S


Classroom-sets of 20 calculators 
in a transportation suite-case 
with charger unit.
"Demonstration Calculators" 
measures: 74 x 37 x 4,5 cm, 
LED21 mm height. 
 M 42 S / M 66 S / 
M 76 S / M 85 S / unilog
M 42 / M 66 / M 76 / M 85

The third generation as cheap calculators:


top S
parat S
unilog S
M 16

Die fourth generation: flat calculators with buttontype batteries and liquid crystal display (made in Japan)


M 300
M 400
M 700
M 800

And at the end ARISTO come on the market with an unusual calculator: a desk-top variant.


R 4000

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© Prof. Dr. Jörn  Lütjens, April 2010