The Comptometers

MODEL 3D11 (1950-1961)

This model has been built from 1950 to 1961 in Chicago, Illinois, USA.

The history of “Comptometer” is very long, started in 1887. The “Comptometer” kept the same functions till 1961 when the production stopped and the brand was sold to a British company.

Learning to operate with this “Comptometer” was not easy, there was a manual with 120 pages to read, and the operator would learn to use both hands to operate faster.

The manual tell that the machine should be placed on the desk in front, slightly to the right, and turned slightly to an angle. The sheets should be placed here on the left. The manual tell that the pen should be held in the right hand with the point away from the operator, to avoid injuries.

If you look at the keyboard, you can see it’s complicated since the beginning. There are 2 numbers for every button, the large numbers are for additions and multiplications, and the small numbers are used in subtractions and divisions.

Very complicated, I’m sorry. But the operators became very fast in doing this, and in some places, till the end of ’60 years, operators were faster than modern calculator operators and didn’t wanted to use other calculators.

No, wonder, if you spend so many time learning a so complicated series of operations, you don’t want to start again studying another calculator!

If you want to see how it works in detail, you can watch the video.

MODEL J (1927)

And this is the Comptometer Model J, from 1927.

Hello everybody.
This is a Comptometer model J, should be around 1927.
It has nice decorations all around.
It's only an adding machine, but with this calculator you can do additions, subtractions, multiplications and divisions.

If you want to have more information you can take a look at the video.

But still it was a very fast calculator, and in doing some operation it was faster than current calculators, since you only had to type the numbers without other keys.