Model B - final step, all assembled

With all the bits cleaned, it's fairly quick and straightforward to put the Comptometer model B mechanism into the case again.

The photo exagerates the whiteness of the keys, they are still fairly grey in reality. The machine however really does look much better than it did:

It still shows signs of its age, with old repairs and old (and new!) refurbishments.

The '3' keys of columns 3 and 4 are not original, but are 1920s replacements. These keys may yet be replaced by new reproductions that are closer match for the composite keys of a model B. These celluloid replacements are however also 'original' and likely a century old themsevles - they are of Felt & Tarrant manufacture and an example of normal repairs that would have happened over the machine's lifetime. 

(The likely reason for these replacements could be seen on the remaining black 3-key. The composite material has ground stone (mica?) mixed with the resin; the black 3-key showed that cracks were starting where porous particles were embedded. It looked like the batch of 3-keys had too-large particles (sawdust?) embedded that weakened the part.)

Also the typeplate is a later, probably 1930s, replacement. It shows a 1921 patent number (for features not on this machine) and looks to be chrome, not nickel. It also shows this is a French machine, exported and sold in France.

Below found image of Comptometer 30680 shows what the original plate would have been, with a 1904 patent as most recent. 

These plates were however already often replaced for export machines, or swapped by the importer, with a localised typelate. Dutch machines often got a neutral plate without patent numbers, with text either in English or in Dutch. In the collection of Comptometers here, one ~1921 model H had just such a plate.

Because the French patent 528,226 of 1921 actually does describe the improved clearing mechanism of the H and would be correct for it, the plates were swapped out between the two machines. (No longer 'original state' now, but the B's plate wasn't original already. Fitting new/different plates and panels was routine during refurbishment of Comptometers, judging the configurations of several observed machines.)

This particular Compptometer was used; the holes for the keystems do have wear. Especially the colum 2 had a lot of 9's entered.

Placing the model B (left) next to a model C-light (right) shows some of the changes made, their development path of Felt & Tarrant. The keys were of course changed from composite to celluloid with a slightly different design and different front panel mounting.

Internally the very noisy B clearing mechanism was completely re-designed in the C (light) and more oiling holes were added to the case (lots of them).

Also an unexpected, small difference is in the subtraction cut-off tabs. On the B they are bent to the right, whereas on the C they are bent to the left. This probably make sense, an improvement - it visually links the tab more obviously to the column it is blocking the carry of.

On a model B the serial number is on the front panel between columns 4 and 5. This model B has serial number 30639 that places manufacture around 1908.

Thinking about that, 1908 is actually quite a long time ago.

Ladies at the Longchamp Hippodrome, Paris, 1908

Looking at it again, it is neat to be able to own and operate such a machine, calculating fine at well over a century old!

Model B - next step, cleaning the mechanism

This Comptometer Model B mechanism had collected an amazing amount of dust and debris. Amazing, because there are not many openings for dust to enter the case of a Comptometer.

It will have taken more than a century, but very nicely settled in dust-towers on some of the rods. Also a lot of debris had settled on the shelf of the bottom slats. This is pretty common, probably dirt that enters via the keystems and perhaps bits of cork lining.

Using a brush, most of the dust and debris was carefully removed. (Unfortunately not quite carefully enough - one small torsion spring fell out of the mechanism! Jolly tricky to get it back into the carry/suppression levers arrangement. Note for next time; brush even more carefully!)

With dust removed, there is some tarnishing, but almost no rust. The carry-suppression of column 8 did not work. Some gentle bending of the 'leg' of the supression-tab was able to fix that.

All the keys had of course been removed. This is fairly simple, unhooking the spring allows the 'wishbone-lever' in the bottom to tilt. This then releases the curved bottom tip of a keystem, allowing it to be lifted out. The keys were kept per column in numbered bags, i.e. all column 1 keys in bag 1.

All were cleaned in the usual way for these. That means, first fine steelwool to remove dirt and rust from the stem. Then wash in lukewarm water with a bit of dishwashing liquid to get rid of steelwool particles. And then a stiff (nail)brush to clean the keys. The lukewarm water will soften the dirt, acculumated grime of decades (century). The picture above flatters the cleaned keys perhaps a bit; they are still grey. But even if not half-as-white as celluloid keys, they are better and no longer dirty brown.

The missing white of several zeroes on the number wheels were re-touched with a light brown latex paint. Starting with cream and adding brown, yellow and black ink until it's a reasonable match.

Compared to later models with the controlled key feature, this mechanism is very open and empty on top. Noticeable is the solid actuating bar that pushes down all the rocker-arms forthe (noisy!) clearing.

A few levers needed to be lifted back onto a notch, but everything seems to be working as it should. Also visible on the frames are bits of cork where the metal had fused to the lining. Ready to be fitted with its top-plate again to fit keys.

Model B - first step, case refinishing

Lovely, decorative scrolls.

Those are the distinctive 'floral' scrolls on the side of the shoebox-style Comptometers. Taking a break from the Marchant Pony B, moved to tackling a Comptometer Model B.

Older Comptometers are becoming rather hard to find, but last year managed to get a Model B for a reasonable outlay. The reason it was reasonable, was that it looked rather bad. It seemed mostly complete, but some 'wrong'  keys, covered in black paint and -judging from clearing handle- possibly blocked. 

Now taking the acquisition out of storage, proceeded to open it up. The clearing handle was stuck solid on its shaft, only heat-cycling (soldering-iron) finally made it budge. As can happen with Comptometers, the mechanism was glued/melted firmly to the case-lining. That took time and force to break it free. After those challenges, it all came apart fairly easily. 

With some columns already taken out in the above image, it's obvious that the machine was painted black without taking off the keys. The dark area of the keys is the original, heavily corroded/patina copper finish. The black paint also was 'irregular' with many specks/spots - that could be rust underneath, but proved to be simply dirt and dust embedded in the paint.

Screws had also been painted-over.

Did not want to leave the case this way; so first removed the old, black paint. Paint can be removed in several ways, e.g. lye or acetone or specialised paint-stripper formulas. With older paints, a least-aggressive method that often works is simply hot water. Much safer than other methods and no problem then to leave the cork+linoleum lining in-place.

In this case hot water worked brilliantly. Place the panel in a container, e.g. a large baking-tray. Then pour boiling water onto it and leave it in the hot bath for about 10 - 15 minutes. The black paint could then be peeled off, revealing the state of the machine at the moment it was decided to cover it in black paint. Some areas still serviceable, but all corners and the top-front panel had been rusty.

Another benefit of the boiling hot water treatment is that the cork-linoleum lining turns soft and malleable. That allowed it to be flattened again, by letting it all cool off with weights (bricks) on the lining.

Fine water-proof sandpaper was used to slightly roughen-up the surface for adhesion and also smoothen rusted areas, then all panels were re-finished in a metallic copper-brown.

Glare makes it hard to get an impression from the above image, but attempted to get the colour within the variations that occur over time with Comptometers. Took a few panels on a trip to the auto-parts store, to select a close, matching metallic lacquer.

In the end, settled on using two spraycans. The Motip colour 51530 is very close, but has too much of a reddish hue. Spraying on a coat of the darker colour 51200 then followed by a coat of 51530 on the still-wet lacquer results in a decent, mix colour with less of the reddish overtones. The slight variations in colour over a panel that result from this 'manual-mixing' were found to be fine, similar variations are found on original panels (from variation in thickness of the original lacquer and from usage too).

The re-finished front-panel here on top of a Model J - it of course varies with different lighting, but overall the lacquer is a credible match.

The decimal-pointers on the front-panel were by the way not taken off, but masked with tape. Between applying coats of paint, the pointers were shifted to different positions. Net-result is that there is lacquer also underneath all the pointer positions (but fewer layers, of course).

After cleaning all the screws, the box was re-assembled and looks much better. All ready for the mechanism to be tackled next.

Platen hardness and type imperfections

With a spare platen salvaged from a wrecked Nr. 5 it was possible to try a variation of platen hardness. The Underwood Nr.5 already had its platen professionally re-covered a few years ago with relatively soft rubber - too soft for typewriter use really, but chosen anyways and types fine. The salvaged platen still had relatively good rubber, properly hard yet resilient. The newly-covered soft platen probably is around Shore 85 and the hard salvaged platen likely Shore 95 or thereabouts.

To start with, a few lines were typed on the machine with its soft rubber and a regular new ribbon; the type widely sold with a relatively coarse weave. (Though not quite as bad as the ribbons sold today for adding machines and/or cash registers - those are coarse and heavily inked too.)

Swapping in the hard-rubber platen and comparing the same lines, it becomes visible that the soft rubber cushions the impact and thus also blurs the type. The hard rubber creates a blacker and crisper imprint. The sound of the typing also is noticably crisper with a hard platen; more a sharp tick than a thud. The overall sound-levels are not all that different, more a change in character of the sound rather than a change in loudness.

The harder platen is less forgiving for any alignment issues of the type. Where the misaligned 'L' typeslug still prints the whole character on the soft platen (the type digs deeper into the rubber / the rubber accomodates the error), the hard platen only prints the top of the character. 

Swapping out the ribbon for a better one with proper inking and a fine weave, this perhaps makes the characters still a bit more crisp. Alignment issues of course show up very clearly too. That's the third test-paragraph on the test-sheet (no backing sheet).

Some forming and re-attaching of the 'L' slug mostly corrected its angle towards the platen, in the fourth test-paragraph it prints better. Not evenly, but at least a complete character. It is still too high and slanted to the left, but correcting that requires specialist bending and/or peening tools for typewriter repair (which we do not have).

From this brief dabbling, optimal hardness for a typewriter platen is probably at least Shore 90. If accepting a more blurry imprint, then a softer platen of less than Shore 90 (but likely (much) harder than Shore 80) can make a machine more forgiving for misaligment and change the sound a little.

(Comparing also with a cork platen; the cork definitely is on the softer end of the scale. Not quite as blurred as the soft-rubber, but certainly less crisp than a proper hard-rubber platen. This was a very hard cork platen, likely dating from the 1940s, and not comparable to cork-sheets available today from craft stores. The plus-side of cork for a platen is of course that it does not harden over time the way that natural rubber can do and will have made sense e.g. when rubber was hard to come by (England in the 1940s); but there is a trade-off with print quality.)

Net outcome, an Underwood 5 that types very decently; with a choice between crisp writing with sharp/loud typing sound and a slightly less crisp with more of a thud/loud typing sound. Swapping platens on an Underwood 5 is not quite as tool-less and easy as on some machines, but with a single screwdriver can be done in a few minutes.

-and also extra understanding of platen hardness and its effect on typing quality.

March 2026 safari - A single Swiss machine from Chemnitz

This morning's visit to the local thrift store, shiny chrome and gloss black amongst the bric-a-brac!

Viewing a bit closer, a Continental Standard in very nice condition - with an extra carriage attachment. Probably for typing cards?

With a QWERTZ keyboard and in French 'MAJUSCULES' on the shift keys.

Its origin is clear from the dealer label; this machine was sold in Lausanne, Switzerland.

Patents on the back (missing / screw-holes for optional tabulator parts?).

Its serial number 477466 dates this Continental to 1931. 

Over irs 95 years it travelled from Chemnitz via Lausanne all the way over to Friesland, now for sale on a table in a local thrift store - and recorded for The Database too :)

Marchant Pony continued tweaks and fixes

The old, battered Marchant Pony is not yet a very good calculator, but improving.

It is looking better than it did originally - and does very stylishly have matching woodgrain handle and baseboard.

To make it still better -or at least nicer- continued tweaking and fixing of the machine. 

The pinwheel drum of the 1920 machine was also completely taken apart, all parts cleaned and re-assembled. This drum does not have a date scratched in, but a stamped number - A977.

Unknown what these codes mean. Similar numbers are found on the check-dials frame, on the carriage and on the carriage-rail, etc. These could be job or order numbers, or quite possibly employee numbers.

Anycase, the 1920 pinwheel parts were placed back into the 1920 machine, using the shaft of the 1919 pinwheel. The 1920 dials were in slightly better condition than the 1919 drum and also (surprisingly) there are several minor design-differences. The donor-machine 1919 drum worked fine, but re-fitting the 1920 dials keeps machine 70049 a little more 'original'. 

Oddly, the 1920 dials fit the 1919 shaft fine, but the 1919 dials do not fit on the 1920 shaft; not quite fitting the key. Another indication that dimensions bach then at Marchant were 'inexact' or perhaps per-batch is that the washer that goes next to the clearing-arm is matched to fit the specific drum-element, like a shim.

The washer thickness is matched to its specific drum-element - in above image shows the different thickness of the washers of the two machines. There must have been a lot of test-fitting and machining of parts to fit in the Marchant factory.

Images of other Marchant Pony calculators online suggested that the grey, thick felt that was still with one of the machines is likely original. The holes for the screws are sloppily cut out, but that may have been done later. This thick felt thus cleaned and placed under the machine instead of the new green sheet.

The donor-machine came with ill-fitting hex-bolts: M6 with an 8.8 strength-marking, they are probably items from the 1960s. The target-machine's original American-thread screws were present, but badly mangled and bent. With a lot of filing, they now do at least fit the thread in the machine base and hold it secure.

These Marchant calculators' baseboards sit on very distinctive rubber feet. These are nailed in place, using four nails per foot. The feet on the donor baseboard were rather damaged, but dimensions could be taken from the surviving parts and a quick CAD model created to make new 3D printed feet in TPU rubber.

The old feet then removed and the new feet hammered into place with similar black nails.

Now not on original feet, but the machine has a less 'gnawed' look and a proper grip again - plus rubber-parts are reasonable items to be replaced at a refurbishment.

Several Pony calculators seen online have a small paper 'notice'  pasted on the baseboard. This baseplate indeed showed signs that something had been glued to it, vague remnants/damage in the lacquer on the front-left corner: probably this specimen also originally had its Six Dont's notice.

This lists of Six Dont's for the user was recreated using images of surviving (bits) of these that can be found online.

The surviving specimens are all very brown - unclear if this is from aging, or if they were brown originally. Unsure of what would be a good color, a range of brownish hues were tried.

Pasted to the baseboard with a starch-based glue - it may yet be replaced with a darker brown. (Starch: warm water should weaken/remove the glue, i.e. reversible.)

This old, battered Marchant Pony is perhaps not a very good calculator, but a great item. It now does work, but not as smooth to operate or reliable as it once would have been. It's a great object for tinkering and this re-building using a donor-machine too gives a lot of fascinating insights into the workings and the manufacture of these calculators, made well over a century ago.

It is a great historic technological item!