Shoebox Comptometers - The Models

Over the years starting in 1886 and ending with the inventor's death in 1930, various 'shoebox' models appeared all with the familiar squared-off copper-colored case. During the next decade, an electric motor-driven model was introduced and the shoebox case was replaced with the "streamlined" look.
Those later designs are covered only briefly on this website.

(Macaroni Box)

The Macaroni box...

This was the original rough model that Dorr Eugene Felt created over the yearend holidays in 1884-85. It was a remarkable implementation of a conjoured design that simply "all came together" at a certain critical point.

Felt's descripton of how it came about...

"It was near Thanksgiving Day of 1884, and I decided to use the holiday in the construction of the wooden model. I went to the grocer's and selected a box which seemed to be about the right size for the casing.

"It was a macaroni box, so I have always called it the macaroni box model. For keys, I procured some meat skewers from the butcher around the corner and some staples from a hardware store for the key guides, and an assortment of elastic bands to be used for springs. When Thanksgiving Day came, I got (home) early and went to work with a few tools, principally a jackknife.

"I soon discovered that there were some parts which would require better tools than I had at hand for that purpose, and when night came, I found that the model I had expected to construct in a day was a long way to be complete or in working order. I finally had some of the parts made out of metal and finished the model soon after New Year's Day 1885."

This one-and-only model today resides in the Smithsonian Museum.
Shoebox Comptometers - General Description

The Comptometer was the first practical key-driven calculator with sufficient speed and reliablility to bring significant economic benefits to the processing of business data. Prior key-driven design efforts had failed to solve the twin problems of over rotation (tendency of a dial to spin past its intended stop) and carry (incrementation of the next higher order on overflow). Felt's design resolved both while adding high speed operation.

Comptometers were available in 8, 10, 12 and even 16-column versions as well as for British money (sterling), fractions, etc on special order. Except for the wooden-cased, A and B models, serial numbers appear next to the "1" key of the leftmost column of keys.

(Wooden case)

Wood cased model...

This earliest and simplest Comptometer was produced from 1887 thru 1903. The very first examples are on display at the Smithsonian Museum in Washington, D.C. and carry no serial numbers. Nearly 90 of these machines are known to have survived with most in private hands. The lowest known "serialized" machine in private hands is #61 and is amazingly preserved. It was auctioned off on eBay on Nov.17, 2001 for $4,388.88. However, machine #71 brought $8601 on Sept 28, 2006, a new record.

This earliest model had round keystems with springs between the keytops and the keyplate. The first examples had keytops of the "typewriter" variety with a metal ring surrounding a celuloid inset containing the character. Near the end of production, composition keytops were used.

The first known use was by the U. S. Treasury Dept in September, 1887 altho it is not known if this was the first true "sale" or placed on loan to gain commerical visability.

( for a list of known "woodies" click here )


The A-model...

Placed on the market in January of 1904 and produced thru September of 1906 starting with serial number 15000. Less than 20 are known to have survived but others may well turn up. Given the fact that less than 6500 of the earlier wooden case models were sold over a sixteen year period, one would expect that no more than 2000 or 3000 A-model machines were produced during its lifespan of less than 3 years making A-models more rare than their predecessor.

The "A" was the first of the steel case models which was to become the standard for the remainder for all "shoebox" models. The design was covered by Patent 733,379 and was a material factor in a later lawsuit with Burroughs. It is distinquished by the novel glass slab dial cover and elongated hanging decimal point indications. "Carry inhibitors" appeared as short protruding tabs for use during complementary subtraction.

With this model, the springloaded keys are replaced with flat stamped metal keystems. The spring mechanism was redesigned being located at the bottom of the keystems inside the case.

A significant new feature dubbed duplex, allowed keys in different columns to be operated at the same time. This made multipiplying a practical operation for Comptometers since shipping and billing almost always involved some quantity times a unit weight or price.

Felt's genius is clearly at work here. Whereas the original model (see above) recorded the keypress on the downstroke, this model recorded on the UPstroke! Beyond this, there were no safeguards and keys had to be given a full downstroke to prevent errors in operation, a very real concern that would not be addressed for another ten years.

Commentary from Bob Otnes...

"The A-model turned the Comptometer from a useful curiousity into a major player in the business world. The duplex feature greatly extended the speed and utility of the device, but it took both skill and training to operate the machine. The book "Applied Mechanical Arithmetic" is one of the most detailed "how-to" books that I have seen for any calculator. No question, the A-model was a major turning point for the company."

( for a list of known A-model machines, click here )


The B-model...

Placed on the market in September of 1906 with starting SN of 25000, the "B" introduced the "lazy-s" register cover which was the final major case change for shoebox Compts. Just below the row of 1-keys were new small, shiney decimal pointers and "thumb-fitted" carry-inhibiters. These were important improvements that improved operator efficiency.

Apparantly some machines had a clean front panel while others carried 4 screws as needed by the A-model to hold the glass cover clamps. It provided no oil holes in the dial cover but had two in the keyplate above the 9-row and one or two on the right side.

The action of the canceling handle was particularly noisy and would produce a factory-like racket in offices when several were in operation simultaneously. It would seem that this model was produced only thru May of 1909 when the next (C) model came on the market.


The C-model...

The "C-regular" started with SN 35000 and was followed 20 months later by the "C-light" starting with SN 40,000. The earliest known "C-reg" has SN 35606 and the earliest "C-light", SN 40137. Some minor mods were made starting with SN 40000 including the introduction of celluloid keys to replace the composition keys employed previously and a lighter key-depression.

As with the B-models, a machine may or may not have carried those useless front panel screws. And for those fascinated by the history of oil holes, the C-light model sported some >>29<< of them in the dial cover and keyplate presumably in response to an almost complete lack in the prior model.


The D-model...

Serials 49,001 to 49,154. Of all production machines, this may be the most elusive, mysterious and rare since only ONE has come to light. This pristine example was discovered in late 2005 by Mike Hancock, a longtime Burroughs repairman and fellow collector.

The serious reader should read ahead at this point thru descriptions of the E-model and F-model to understand what follows and return here to continue this description.

For all the world, the D-model looks exactly like the F-model. Well, not quite. Like Sherlock Holmes' "dog that didn't bark", the visual clue is the missing "Controlled Key", normally found next to the 9-key of the rightmost column. A second clue is that the D-model machine is a full 2 lbs. lighter than its F-model cousin, each of its 8 columns having a quarter of a pound fewer parts. Both in cost of parts and assembly labor, it was surely cheaper to produce.

Since no more than 153 of this model were ever made (and only this one** example has come to light), one could speculate on why it was produced at all. A reasonable theory is that (ignoring the ill-fated E-model) the "D" and the "F" machines were introduced simultaneously at different price levels, both somewhat higher than the C-model being replaced. For customers who felt the Controlled Key feature might not be worth the extra expense, the D-model was available, at least for a brief period. It was probably dropped from production due to lack of demand as the Controlled Key was highly favored by Operators.

**Prior to the discovery of this lone example, I speculated on the nature of this mystery machine at length(Engineers) , believing it to be simply a special application of the E-model. Happily, I have been proven wrong.


The E-model...

Arriving in 1913, this short-lived model could easily stand for "elusive" as I am aware of only 10 with one other reported in eastern Australia. While reportedly "on the market" from March of 1913 thru May of 1915, the relatively small number of survivors would indicate that this model was less than a roaring success. It was introduced with one of the earliest color ads and appeared on the back cover of the Aug 24, 1913 issue of Sunday Magazine of the Chicago Record-Herald

Exactly what made Felt abandon this machine is unknown. It may well be that it proved too expensive and/or too trickey to manufacture. And/or field maintainence could have become a problem as the odd keytops may have broken more easily under heavy and constant use.

For a detailed discussion of E-model serial numbers, patents, mechanical anomolies, etc, click here.


The F-model...

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.


The G-model...

No G-model was ever marketed and, indeed, may never have existed. The discovery of one of these would be a truly remarkable find. The only documented indication I've ever discovered is a passing reference in the 1919 H-Model Repair Manual.

One possability is that it was prototyped as an earlier, perhaps quite different (maybe very different) design of the H-model clearing mechanism. A machine exists that seems to give some credence to that explanation.


The H-model...

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.

The I-Model...

Here's another model that never existed. It is easy to speculate that the "I" was simply passed over to avoid any confusion with a "1" digit.


The J-model...

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).


The SuperTotalizer...

Introduced in the early 1930s, SNs were intermixed with J-models as orders entered production. Certainly an unusual looking machine, it has sub-total/grand-total capabilities similar in design to that of the Mechanical Accountant, a machine designed "around 1900" (according to Ernst Martin) by J.A.V.Turck who appears to have been employed by Felt & Tarrant from about 1910 thru the 1930s.

In Sept of 1921, Turck received patent #1,391,220 (assigned to F&T, of course) for the basic design. Another patent issued in Sept of 1930 (# unknown) to Turck probably covers the "leading blank suppression" shutters that became standard on the later M-models.

The other patent appearing on the machine (#1,886,883) was issued to W.S.Johnson of Providence, RI in Nov of 1932 (filed over 11 years earlier). One wonders what connection there must have been since this design is similar to the Mechanical Accountant which Turck is said to have invented while living in Providence some 30 years prior.

This model is sometimes referred to as "duplex" because of the sub-total and grand-total registers. Such reference should not be confused with the duplex feature introduced with the A-model which allowed simultaneous depression of keys and was a significant operational feature (see above).

The machine pictured exhibits a strange "oozing" of the digits imprinted onto the light colored keytops. It seems that this problem affected only some machines produced in the 1930s and perhaps was due to a chemical interaction between the mastic used for the numerals and the keytop material.

Apparantly very few SuperTotalizers were ever made as only four or five have come to light.


Refurbed machines...

Like the Supertotalizer that extended the shoebox line of Comptometers past the year of Felt's death, after WWII, programs were initiated in Great Britain and the Commonwealth to refurbish an unknown number of these older machines. Some belonged to customers and were returned in "like new" condition while others were taken as tradeins on newer models and put to service as rentals by F&T.

Ray Mackay describes the process as it took place in Australia...

(ed note: extensively edited from email exchanges)
"During a difficult financial period (in the British Commonwealth), Comptometer distributors refurbished the older square (shoebox) models. Those had the copper plated case sprayed with a brown translucent lacquer.

"Before any respraying, the case was removed from the silver base plate (I'm not sure if the four case sides were separated) and the decimal indicators from the register cover. Also, all cork was removed from everywhere as cork does not like the ovens used for the enamelling.

"Factory reburbishing was a professional job. The new colour for the keyplate was smooth green baked enamel and baked wringle finish on the four side plates.

"The keyplate was removed as well as the little decimal pointers of the register cover. The decimal indicators and patent plate would be replaced. All cork lining was removed and later, replaced being refitted with new rivets.

"Where the keyplate was worn, it was replaced with a new one. Where it was in good condition, it was replated and the old serial numbers transferred to the new keyplate.

"On such factory/distributor rebuilds, the keytops were removed (whilst the machine was disassembled) by placing the keystem in a vice, removing the keytop with a specially designed forked lever and hammering on a new 3D11 extruded keytop with a leather mallet (the jaws of the vise were lined with copper to stop indentation on the keystem by the vise).

"The machine was stripped down to the frame and checked for chipped teeth on gears, worn bearings, pitted or grooved shafts, etc. The individual parts were washed in 'Shellite' and re-oiled as the machine was assembled.

"Prior to key fitting, all trigger mechanism adjustments were made so that the machines clicked over like a Swiss clock. The keyboard was then fitted and the keys reinstalled. Next, the machine was tested for a week by skilled operators before being returned to the customer or placed in rental service. Any machine found unsatisfactory was reprocessed at the trigger adjustment phase. This was because trigger adjustment relied on the accurate position of an eccentric bush that positioned the segment lever before any adjustment was made. The bush was adjusted to position the bellcrank accumulators stop correctly in relation to the accumulator's lantern pins. As you are looking from under the accumulators it was not always easy to get the adjustment right on.

"Cases finished in Black or by lesser standards may have been processed by second hand office equipment dealers or even performed by other companies on 'trade ins'. The official 'rebuild' was a thoroughly professional job and final testing before the keyplates were fitted was performed by the service manager.

"The import restriction into the U.K. had an impact and the Comptometer place in Deansgate in Manchester did rebuild machines. There, the standard Felt & Tarrant policy would apply.

"If you can find a Les Langley in the UK that worked on Comptometers he would know the Deansgate details. We also had a Don Rosier in Adelaide who was factory trained at Deansgate and is now a Doctor in South Australia. I contacted him a few times, as a friend, however I am afraid his interest in his past is not to high on his priorities."

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