Comptometers by the Felt & Tarrant Manufacturing Company

A "J" model, our first comptometer (indeed the first artifact in the Digibarn collection acquired back in 1987)

The comptometer has an venerable place in the Digibarn physical collection: it is the very first artifact acquired for the collection, back in the late 1980s at a yard sale for $10. In fact it could be argued that this beautiful copper and brass box was partly the inspiration for the collection, together with the final public demo of the Xerox Star 8010. At the time I didn't know anything about it except that it was a thing of beauty. I cleaned it as best I could and wondered about the insides. There seemed to be a place for a crank which I didn't have, and the keys were stuck. Still I was fascinated by the dates on the stainless steel nameplate, which listed the first patent date as 1887! As it was in 1987 that I acquired it, I felt it was "the first personal computer" of the Victorian era.

All during through that period of my life in the 1980s and 1990s the "compt" followed me around, through multiple moves, and ended up at Ancient Oaks farm in the summer of 1998. It wandered into the Digibarn one night and became the first machine in the collection which was to explode in size over the next few years.

From Wikipedia's definition of comptometer:

A Comptometer is a type of mechanical (or electro-mechanical) adding machine. The comptometer was the first adding device to be driven solely by the action of pressing keys, which are arranged in an array of vertical and horizontal columns.

Comptometer is, strictly speaking, a trade name of the Felt and Tarrant Manufacturing Company of Chicago (later the Comptometer Corporation), but was widely used as a generic name for the class of device. The original design was patented in 1887 by Dorr Eugene Felt, a U.S. citizen.

Although primarily designed for adding, division, multiplication and subtraction could also be performed. Special comptometers with varying key arrays (with from 30 to well over 100 keys) were produced for a variety of purposes, including calculating currencies, time and Imperial measures of weight.

In the hands of a skilled operator, comptometers can add numbers very rapidly, since all the digits of a number could be entered simultaneously using as many fingers as is required, making them much faster than using an electronic calculator. Consequently, in specialist applications they remained in use in limited numbers into the 1990s, but with the exception of a handful of machines, have now all been superseded by the use of computer software.

The story of the Felt & Tarrant Comptometers as told by Comptometer Expert Brooke Boering

Brooke Boering is one of the world's experts and greatest collectors of the comptometer. You can glean a bit of what he knows by visiting his website Comptometers - Biography of a Machine or by hearing and seeing him talk about them below. Also see Brooke's bio here.

Image of Brooke (on right) giving us a tour of the comptometers	Digibarn Radio audio piece: Brooke Boering on Felt & Tarrant and the comptometers
	Digibarn TV video piece: Brooke Boering on Felt & Tarrant and the comptometers

Click on the links above to listen to or view Brooke Boering telling the story of the Felt & Tarrant company and its comptometers.

Click here to read more about the Felt & Tarrant Manufacturing Company.

The Digibarn's Felt & Tarrant Comptometers

All four of the comptometers donated by Brooke

Comptometer up close!

Brooke's notes on the donations

"F" Model

From Brooke's excellent site Comptometer, Biography of a Machine:

Arriving in May of 1915, with starting SN 100,000, this machine was destined to bring volume production to the F & T factory. If machines were produced in strict sequence, sales of F-models would appear to have outpaced all previous models combined. It was in production thru the end of the decade, some five and a half years.

A major feature was the presense of the "Controlled Key" (introduced on the ill-fated E-model) which locked the keyboard when any key was not fully depressed. Since these machines were operated very rapidly by trained operators, the ability to detect a partial stroke AND allow for immediate correction without losing the running sum, they were warmly received. It may well have been the principal reason for the great popularity of this model over its lifespan.

Again, the arrangement of oil holes was altered with this model, now having a single set of "bare" holes across the dial cover, an added set of "eyelet" holes just under the 1-row and 12 of the eyelet type above the 9-row with no holes on any side panels.

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"H" Model

Brooke notes that this may be the oldest surviving H model. From Brooke's excellent site Comptometer, Biography of a Machine:

The venerable "H"appeared in 1920 as F&T's first postwar (WWI, that is) model with starting SN 200,000. It is easily distinquished from prior models by the presense of the "Comptometer" script logo on the front and back of the case. However, improved operational characteristics were to largely determine its fate in the marketplace.

The forward placement of the clearing lever allowed the operator to zero the register with a single motion of the little finger without altering her hand position over the keyboard. Internally, less obvious improvements included audible, tactile and visual clear signals (bell, key pressure and slight offset of register zeros). All these refinements improved operator speed and accuracy but at some cost in complexity of the mechanism which required the front of the machine be extended by about 1/2". Support for this major step forward included one of the most detailed technical manuals for mechanical devices ever produced.

By 1920, Felt & Tarrant had grown into a major presence in the office machine business and Dorr Felt would "kick off" the introduction of his new model with a gathering of his sales force in June at the Chicago factory. The H-model was a big hit with users and justifiably so what with its many operational and aesthetic improvements. It was produced until early 1926.

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"J" Model

From Brooke's excellent site Comptometer, Biography of a Machine:

The final mass-produced shoebox model was the long-lived "J" that first appeared in February of 1926, and seems to have started around SN 245,000. Clearly intended to replace the H-model, it was set off visually from its predessors by its green keys which replaced the traditonal black. However, this distinction is not a reliable model indicator since keystems on F, H and J models were identical and repairmen often simply replaced keys with what was in their bag.

Altho the "J" had no major new features, many operational aspects were markedly improved and it received wide acceptance in the late "roaring 20s". The model was in constant production until the start of WWII concurrently with the newer electric (K) and "streamlined" (M) models. Many of the survivor examples were still in operation at major U.S. corporations until the late 1970s, a remarkable record spanning some fifty years of useful service.

Interestingly, the "J" was the only shoebox model to carry its alpha designation next to the serial numbers. And, according to Tom Thornton, F&T employee (1942-52), "the left two digits of the serial number was the year of manufacture" (except for production in postwar England).

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"K" Model

This model is a bit of a departure for Felt & Tarrant as it is styled much differently than the previous models and it is electric motor driven. This model was produced in the 1940s.

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CIMG2831.JPG	CIMG2832.JPG	Electric power socket
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And last but not least...

Our original "J" Model Comptometer

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See Also:

Brooke Boering's site: Comptometer, Biography of a Machine
and the Felt Estate Restoration Project, the new home for many of Brooke's comptometers

Digibarn TV video piece:
Brooke Boering on Felt & Tarrant and the comptometers

Digibarn Radio audio piece:
Brooke Boering on Felt & Tarrant and the comptometers

Our Wolverine toy adding machine (a kind of baby comptometer)

Other Comptometer and Felt & Tarrant sites around the net:

Comptometer pages at Vintage Calculator Web Museum including instructions
on how to operate a comptometer

Java applet simulating a comptometer at the Calculating Machines site

Comptometer defined at Wikipedia

NYU page on Felt's printer

Ray Mackay's Comptometer Memorized Notes including detailed descriptions of how they work