Jaap's Mechanical Calculators Page

Rapid Computer / Comptator

Rapid Computer, in box

The Rapid Computer
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The Rapid Computer

This is called a Rapid Computer. This particular one was made between 1906 and 1908 in Michigan. Its outer case is made of nickel-plated brass, and it has 9 vertical brass sliders at the top, which you control with a stylus. Further down is a celluloid window showing a 9-digit register, which is a row of 9 number wheels on a common axle. Each slider has the numbers 1 to 9 on them, and to add a number to the register, just put the stylus on the correct digit for a column and slide it down until the stylus hits the stop bar. When you release the slider, it springs back up to its original position, and the corresponding register wheel will have increased by your chosen digit. The register has a carry mechanism, but it can be difficult to execute a carry when several numbers have to roll over because it does not use stored energy.

There is a clearing knob on the right, on the axis of the register. To clear the register you have to pull out the knob slightly to unlock it, and then turn it anti-clockwise almost a full turn. This resets all the number wheels. You must then turn the knob clockwise back to its original position, where it will lock into place. If the knob is not returned, then the register will not correctly perform carries.

Rapid Computer, box
Rapid Computer, box
Rapid Computer, in box
Rapid Computer, in box
Rapid Computer
Rapid Computer, sliders
Rapid Computer, stop bar
Rapid Computer, inscription
Rapid Computer, register
Rapid Computer, clearing knob
Rapid Computer, top
Rapid Computer, right side
Rapid Computer, left side
Rapid Computer, bottom
Rapid Computer, bottom
Rapid Computer, pick stylus

It has serial number 3198, which is stamped on the front, along with the text "THE RAPID COMPUTER CO. / PATD. 1892". Further text is hard to make out, as it has worn away and probably was stamped in very poorly in the first place, but above the serial number it used to read "Benton Harbor, Mich.". Later machines have the line "Other Patents Pending" below the serial number but this one probably did not.

It comes in a nice storage box, and with a stylus. The stylus seems to be a nut pick made by H.M. Quackenbush, inc. of Herkimer, N.Y., so does not belong to this machine. It is hard to tell how old the nut pick stylus is as Quackenbush made them for many decades, but it looks the part.

Rapid Computer, opened
Rapid Computer, open register
Rapid Computer, working
Rapid Computer, clearing knob
Rapid Computer, clearing knob
Rapid Computer, clearing knob
Rapid Computer, top cover
Rapid Computer, window

This machine is often classified as a chain adder, but it actually uses toothed racks, a bit like the Stima does. When you push a slider downward, it travels over the top of its corresponding number wheel, and the ratchet teeth underneath the slider push that wheel around. When you release the slider, it is pulled back up by a spring without moving the wheel back.

The original patent makes it clear that the width of the columns exactly matches the width used in bookkeeping ledgers, so that one could place the machine on the page and exactly line up the sliders when entering the numbers, thereby reducing mistakes.


Below is a video I made that demonstrates the Rapid Computer.


This machine was invented by Peter J. Landin from Minneapolis in the early 1890s, and he received a patent in September 1892. Apparently he set up a company, the Landin Computer Company, to produce it, though it is not clear to what extent this "Landin Computer" was actually made and sold, since almost none seem to be in existence now. He filed patents for a cash register around the same time ( US 526,400 / US 526,401 / US 526,402 ), so he may have concentrated on commercialising that. He later has patents for a phonograph ( US 1,422,453 ) and for subtitling films ( US 1,234,046 ).

Some ten years later it was marketed again, and this time much more successfully. The Rapid Computer Company of Minneapolis sold it as the Rapid Computer. In 1906 they moved to Benton Harbor, Michigan, and around this time the design was improved slightly by the addition of a sturdy stop bar for the stylus to bump into at the end of its downwards movement. In 1909 the company apparently relocated to Chicago, operating from the Tribune building. Baker-Vawter, a company making office filing equipment, were also based in that building. It seems that the Rapid Computer Company became part of Baker-Vawter, or maybe Baker-Vawter merely took on the distribution of the Rapid Computer at first. In 1914 the Rapid Computer Company was operating from Benton Harbor once again, but note that some of the machines produced at this time are stamped with the Baker-Vawter company name. The advertisements seem to dry up soon after, and the Rapid Computer Company may have dissolved then. I found some adverts in 1917 for the Rapid Computer, now sold through an agent in Louisiana, but these may have been left-over stock. I also found that in 1919 Baker-Vawter had a metal plant in Benton Harbor, so I would speculate that the manufacturing of the machine was done there all along, that Baker-Vawter bought the Rapid Computer Company for its metal plant, and eventually had it produce other equipment.

Here is a table showing the dates for which I found advertisements, with the addresses used in those ads. It also lists some of the serial numbers seen in pictures or text I found online in collections and auctions. From the serial numbers it seems likely that the Rapid Computer Company first started a few years before 1905.

Time periodCity/stateAddressSerial Numbers
July 1905-April 1906 Minneapolis, MN641 Andrus Building / 30 Bridge Square 1706, 1822
October 1906-March 1908 Benton Harbor, MI35 Lake Shore Road / 271-283 Lake Shore Road 3150, 3198, 3328, 3729, 3807, 3938, 4047, 4328, 4362, 4566, 4568, 4828, 5000, 5015
May 1908-March 1910 Chicago, Ill.1418-2089 Tribune Building 5379, 5590, 5665, 5817, 6100
March 1914-May 1914 Benton Harbor, MI117-317 Computer Building 6150, 6173, 6303, 6403

In Germany in 1909, the Rapid Computer was improved upon and renamed the Comptator. When entering a number in the Comptator, the slides remain in the downwards position. This allows you to see what number you entered. Only by pressing a button on the left side of the machine are the sliders released. That release button can also be locked down so that the machine acted like the original design, which allows for some simple multiplications by entering a number several times in succession. This same functionality can be seen on for example Seidel und Naumann's SuN adder.

The Comptator came in 9 or 13-column variants. It was made by Schubert & Salzer, a company based in Chemnitz, which mostly specialised in making machines for the textile industry, e.g. spinning machines or machines for spooling thread. In about 1922 the company stopped making these calculators, and the production was taken over by Hans Sabielny in Dresden, still using the name Comptator. The exact relationship between Sabielny and Schubert & Salzer is not clear to me, though. Several websites claim that it was he who made the improvements to the Rapid Computer, and that he had Schubert & Salzer manufacture the machines for him. Note however that the 1909 patent containing the improvements is assigned to Schubert & Salzer (German patents do not list the inventor, only the assignee), and the US equivalent patent lists Woldemar Reinhold Heinitz as the inventor.

The company Schubert & Rother from Dresden had also started making a variation of the Comptator called the Surot, for which they received a patent in 1919. In 1921 production went to the company Cosmos Büromaschinen Berlin, and the calculator was then called the Addi-Cosmos. A year later production was by Bergmann Universal GmbH, with the calculator being called B.U.G.. I don't know if these are three different companies, or one company that changed its name. Production stopped in 1924, at which point Bergmann Universal produced other calculators instead.

Another Comptator clone was the Addo from Sweden, and there are probably more.

Articles and Advertisements

I have not found any advertisements relating to the Landin Computer in online archives, but there are quite a lot for the Rapid Computer. Note that the number in the contact address for the Rapid Computer Company could change depending on where and when the ad is published.

Below is a representative sample.

1905-07 business man's magazine
1906-04 McClure's
1906-09 business man's magazine - baker-vawter
1906-10 business man's magazine
1906-11 business man's magazine
1907-05-19 Evening star
1907-07 Success Magazine
1907-07-07 Evening star
1907-09-15 New-York tribune
1907-10-12 The Literary Digest
1907-11-24 Evening star
1907-12 Busyman's magazine
1907-12-14 scientific-american
1908-01-26 Evening star
1908-03-21 scientific-american
1908-05-02 scientific-american
1908-05-24 Evening star
1908-06-06 scientific-american
1908-08-17 Grocery world
1908-09-12 The Literary Digest
1908-09-26 Colliers
1908-09-28 Grocery world
1908-10 McClures
1908-12-12 Colliers
1908-12-12 The Literary Digest
1909-01 Popular Mechanics
1909-01-09 Colliers
1909-01-16 scientific-american
1909-02 The Pacific monthly
1909-02-20 Colliers
1909-04 Pacific monthly
1909-06-19 Collier's
1909-06-19 scientific-american
1909-07 Pacific monthly
1909-07-17 scientific-american
1910-03-05 Colliers
1914-03-14 The Literary Digest
1914-05-02 The Literary Digest
1914-08-03 Evening Chronicle, Marshall, Michigan
1915-10-15 The Sydney Morning Herald
1915-11-13 The Sydney Morning Herald
1917-03-31 Abbeville progress
1917-10-06 Abbeville progress
1917-11-17 Abbeville progress

There are a few advertisements for the Comptator as well.

1910-09-07 Berliner Tageblatt
1911-08-16 Berliner Tageblatt
1912-11-06 Berliner Tageblatt
1917-07-04 Algemeen Handelsblad
1917-09-14 Algemeen Handelsblad

Here are some articles related to these machines.

1892-09-08 St. Paul daily globe
1925 Ernst Martin 1
1925 Ernst Martin 2
2005-02-02 Creative Close Ups


PatentFiling datePublished dateNameDescription
US 482,31203-02-189106-09-1892Peter J. LandinLandin's Computer
DE 221,39612-01-190928-04-1910Schubert & Salzer Maschinenfabrik
(Woldemar Reinhold Heinitz)
Comptator input release mechanism
See also: AT 52,251 B; CH 50,980; FR 410,777; US 1,020,200
DE 322,50825-03-191901-07-1920Oskar Rother; Karl HeindelImproved input release mechanism.
(used in Surot / Addi-Cosmos / B.U.G.)
DE 395,39929-05-192119-05-1924Hans SabielnyComptator variant


Rechnerlexikon has a page for the Comptator and has some material about the Rapid Computer.
Rechenmaschinen-Illustrated has a Rapid Computer, a Comptator, and an Addi-Cosmos and a B.U.G.
Rechnen Ohne Strom is an interesting site that has a page about toothed rack adders.
The history of Computing has a page about Peter J. Landin
Christian Hamann has a page showing a 13-digit Comptator
Rechenwerkzeug.de has the German Comptator Manual.

© Copyright 2018 Jaap Scherphuis, .