As I indicated in the video, there were various versions of the Corona 3, including some with an integral carriage return arm, rather than the pinch-style of this one. Some also had automatic ribbon reverse, whereas this one has the S-curve ribbon threading path (where the ribbon threads counterclockwise on the left spool and clockwise on the right) and the spool nuts are used for manual reversing -- the nut is tightened on the intended takeup spool and loosened on the intended supply spool. It certainly gives you the feeling that you're intimately involved in the machine's operation, reminding me of a manual-transmission car.

There are 28 typebars on this model, though some international versions had up to four additional "dead-key" typebars for accent symbols. These machines also came in a variety of colors, though black was by far the most common.

The heritage of the Corona 3 comes from the Standard Folding version, made by the Standard Typewriter company from 1906 to 1912, when the company was renamed Corona. In 1925 Corona merged with L.C. Smith to form L.C. Smith & Corona Typewriter Inc.

Robert Messenger has a nice article on his blog about the history of the Corona 3 folding typewriter tripod, here.

The July 1988 edition of Et Cetera magazine has a detailed article about the Corona 3, here; and the June 1990 edition has an article about the designer of the Corona 3, here.

It was certainly fun to read back into the early days of typewriter collecting, in these back-issues of Et Cetera; wherein they recommend the Corona 3 as a good "starter" machine for neophyte collectors, due to their commonality (the collector market has certainly changed since then).

Using the Corona 3 in Practice

So, what's it like to actually use the 3-bank Corona? If you're a touch-typist, you'll find it necessary to place your right pinkie finger atop the right FIG shift key, since there are no other keys to the right of the "L". In fact, Corona made an accessory finger-support bracket for just this purpose, that clamped to the right frame member (these are about as rare as the telescoping tripod). Aside from that, I find myself typing more pedantically, using a slower, more deliberate keystroke. Part of this is so I don't outrun the machine, but also because I'm less than accustomed with the locations of the various symbols, and the necessary use of the FIG shift keys. I've made numerous typos due to instinctively hitting the CAP shift instead of FIG shift when accessing the more commonly used symbols.

Just to refresh the reader's memory, for every key except the bottom right two (,&, and .), unshifted gives you lower case letters; CAP shift gives you upper case letters; FIG shift gives you symbols and numbers. For the ",&," key, unshifted is a comma, CAP shift is the ampersand (the sole exception to symbols being accessed via the FIG shift key), while the upper comma is accessed via the FIG shift key. For the lower-right period key, all three positions yield a period. The apostrophe is a FIG shifted J, while the question mark is a FIG shifted C (which leads me to pretend that the word "question" begins with a c-sounding phonetic, just as a memory aid).

Yes, you'll require a bit of practice in order to get accustomed to the 3-bank keyboard. But yesterday I typed three full pages on the machine, what I call my typewritten journal (essentially anything typed for no other specific purpose), and I found the experience pleasant. What I noticed was my "speed of thought" -- limited by those frequent pauses required to gather my ideas into sentences, as I compose directly onto the machine -- are slowing me down more than the machine itself, or my inexperience with the keyboard layout. This might not be true were I merely transcribing text, doing what might be called secretarial work. But for rough-draft composing, the Corona 3 presents little in the way of limitations.

As I perused various websites late last night in search of more historical information on the Corona 3, I kept coming across this image, of an officer typing on the 3 using the folding tripod. Knowing my fumble-fingers technique was barely adequate to the task, as I remain less than fully versed in the keyboard layout, it got me wondering how an officer, such as the one in the photo, would get along with the machine. He appears to be using a touch-typing technique, rather than two-fingering his way across the keyboard; and I'm assuming military discipline would require error-free text. Did he have some eraser pencil handy? Was he permitted the luxury of strike-through corrections on official reports? This got me to doing a bit of searching, and I came across archives of what were essentially daily action reports. Here's one example:

You'll notice the correction made on the third line from the bottom. So it certainly seems that typos, to a certain extent, were tolerated in these daily action reports. Perhaps they would be retyped later at some divisional unit command level.

I also did a bit of searching through PDF files of US Army officers manuals, looking for the topic of typing etiquette, but came up empty before the hour got late and it was time for bed.

Though my machine is from 1929 and not The Great War, I feel some kinship with those officers and men who knelt over their typers, making reports on the day's combat. I certainly feel blessed that I can do so in the comfort and peace of my home.

By now you know I've been an abacus aficionado for most of my adult life. Yet, despite the oddball nature of bead-frame calculators in the 21st century, I've met a number of people over the years who were actually interested enough in learning basic abacus addition to make an honest effort. Invariably, many of these adult learners would struggle with the concepts, never gain proficiency and eventually lose interest.

I was one of those adult learners who also struggled with some of the concepts, until I met a school teacher in Socorro, NM, a Taiwanese native and abacus user since her formative years, who showed me a few key concepts that made the Japanese soroban style of abacus much easier to use. In so doing I also noticed that the concept I struggled with was one she took for granted, having learned the soroban in her formative years, when the cerebral cortex is much more malleable. I soon realized that part of the problem was the nature of adult learners such as I.

My interest in the abacus waxes and wanes over the years, interspersed as it is with many other passions. Recently I've come to reconsider the problem of adult learners of the abacus, since I currently have an exhibit of my abacus collection on display at a local public library, and have been working to simplify the teaching of addition on the Japanese-style soroban.

The problem presented by the abacus is you have a limited number of beads available to represent numbers, thus when adding numbers together you frequently run out of beads, necessitating roundabout methods of completing the problem. I realized the seasoned abacus operator intuitively recognizes these various situations, on-the-fly, and immediately responds with the appropriate technique almost subconsciously, through rote training. What I immediately set about doing was documenting those various instances when alternative techniques are required to complete a calculation, with the goal of systematizing a formal methodology for approaching any addition problem.

Naturally charts and graphs would be employed, as I can imagine Arlo Guthrie explaining in his classic piece Alice's Restaurant Massacree: "...twenty-seven 8-by-10 color glossy pictures with circles and arrows and a paragraph on the back of each one explaining what each one was, to be used as evidence against us..." So be forewarned about the color glossy pictures ahead!

As I said, I've been using the abacus for years, with proficiency sufficient for basic addition, and thus I had to slowly unravel my thinking process of how I approach these problem situations. I started by mapping all of the possible addition problems and color-coding them with their requisite solution technique.

Figure One:

Addition problems on the soroban require four general categories of response. The first category, where the cells in the above chart are white, are direct-entry problems where no special technique is needed. Simply enter the starting number (indicated by numbers along the left column of the chart) and then enter the addend (indicated by numbers along the top of the chart) and the answer presents itself on the soroban.

Here, these direct-entry problems have been isolated from the rest of the cells:

Figure Two:

The second category of problem response are when adding numbers together that are both less than five, but there aren't enough beads on that rod to complete the problem. These are indicated by the cells highlighted in yellow, and marked with a "5" in Figure One. These cells are isolated in Figure Three, below. The solution of these problems require the employment of what are termed "fives complements."

Figure Three:

The use of complementary numbers is a technique designed to get around the problem of running out of beads to complete a calculation. Instead of adding the number, we subtract its complement and add the next higher bead. Consider the following table in Figure Four:

Figure Four:

The top row lists the digits 1 through 9, and the following two rows list the tens complements and fives complements of each number, respectively. The five complement of a number is a number that, when added to the original number, equals five. Similarly, the ten complement of a number is a number that, when added to the original number, equals ten. It is a requirement that the abacus operator know by heart both the fives and tens complements.

So, in this second category of problem the solution is found by adding a five bead to the rod and subtracting the fives complement of the number, in one swift downward motion of the index finger.

The third category of problem response are those whose solution is found by employing a tens complement operation, as indicated by the green cells in Figure One. With these problems, the tens complement of the addend are subtracted from the rod, then a single ("ten") bead is added on the next rod to its left. These problems have been isolated in the chart in Figure Five, below:

Figure Five:

There is a fourth category of response, indicated by the rose colored cells in Figure One, and isolated in Figure Six, below. These kinds of problems were the ones that I stumbled to understand, as they are ostensibly tens complements problems but require a fives complement operation to also be performed; what I call "nested" or "combined" complements problems.

Figure Six:

The shortcut method my abacus teacher taught me for solving these kinds of problems was to "push up" the number, then add the single ("ten") bead on the rod to the immediate left (instead of thinking of it as a fives complement problem nested within a tens complement problem).

In addition to categorizing the soroban abacus operations into four categories of response, I had to decipher in what order I tend to solve them in my mind; since I often solve the simpler problems automatically, with little conscious thought. In so doing I devised a checklist, in the form of three questions I use to interrogate a problem, resulting in the four possible response methods.

Figure Seven:

By following this checklist in the order suggested, the simplest solutions are arrived at first, followed by solution methods of increased complexity. I've found that following this sequence of questions always leads to a solution every time, but there are two additional complexities to unravel before we can call this bulletproof.

The last two solution methods involve tens complement operations, where a single ("ten") bead is added on the next rod to its left. However, there are two situations where that single ten bead cannot be entered.

Figure Eight:

As you can see from Figure Eight, above, if the rod to the immediate left of our problem is either a four or a nine, there will be insufficient beads available to complete a tens complement operation. In the case of a four, all the beads on that rod are lowered, while in the case of a nine, that rod is cleared and the single bead is added to the next rod to its left.

This is essentially all that one needs to know in order to master addition on the soroban. However, there are a few things I've left out, assuming you already knew them. The first is how numbers are entered. The abacus is "cleared" when the top and bottom beads are pushed away from the dividing bar. Numbers are entered when they are pushed toward the dividing bar. The four beads below the bar are each worth one point, while the single bead above the bar is worth five points.

Secondly, numbers are entered on various rods in place-value fashion, similar to how numbers are written on paper. For addition, multidigit numbers are summed from left to right instead of the more usual right to left. When adding multidigit numbers, each digit is treated as a separate single-digit problem, using the rules outlined above.

Finally, proficiency is only gained through constant practice. One easy practice method is summing the number sequence 123,456,789 ten times. In the process, every possible combination of addition problem will be encountered. You can easily tell if you've arrived at the correct answer because it should be: 1,234,567,890. This lengthy number should be compatible with any soroban having at least ten rods.

You can also use your grocery store and shopping receipts as another kind of practice problem. Add up the prices listed on your receipts and they should match the store's subtotal. This is a good way to bring some fun into the drudgery of shopping, as you look forward to adding up the receipt totals afterwards.

I've presented these techniques in a comprehensive video, embedded at the top of this article. My intent is, by following this method, addition on the soroban can be mastered by the average adult learner with but rote practice to gain proficiency and speed. I hope you will consider becoming an abacus practitioner.

Post-Script: I'm frequently asked for links where people can buy a soroban-style abacus at a reasonable price. Keeping in mind that artisanally-crafted Japanese soroban are works of art and their construction methods an official national treasure, I've found some inexpensive Chinese-made versions with beads sufficiently large for the adult westerner. Here is one such example: www.shorturl.at/tvwM8

Japanese 1:5 Soroban with kanji characters on the dividing bar representing denominations of yen.

Central Asian Schotty, 10-bead abacus

10-Bead school abacus of the kind Napoleon brought back to France from the 19th-century Russian campaign.

Here are the presentation foils included in the exhibit:

The following pages illustrate examples of abacus addition. First is how numbers are represented on the 1:4 soroban:

Next are two simple addition problems, the first one direct addition, the second using fives complements. But first I should explain the concept of "complements."

Since there are a limited number of beads on each rod, there are occasions when you can't directly add a quantity of beads. For numbers under 5, these problems are known as "fives complements." A five complement is a number that, when added to the original number, equals five. For example, the fives complements of 1,2,3 and 4 are: 4,3,2 and 1, respectively.

There are also tens complements of numbers: a number which, when added to the original number, equals ten. The tens complements of 1,2,3,4,5,6,7,8 and 9 are: 9,8,7,6,5,4,3,2 and 1, respectively.

The way that fives complements are used in addition is, instead of directly adding the number (which you can't, because there aren't enough beads left on the rod), you subtract the fives complement of the number and add a five bead from above the bar.

The way that tens complements are used in addition is, instead of directly adding the number (which you can't, because there aren't enough beads left on the rod), you subtract the tens complement of the number and add a single bead on the next rod to the left.

Next is a problem involving both fives and tens complements. These problems happen when you have to do a tens complement operation, but there aren't enough beads on the rod to subtract the tens complement. The shortcut method my Taiwanese abacus teacher taught was to "push the number up," as illustrated in the next foil, where in order to add 7 to 6, you "push the 7 up":

The photo below shows the classic book on Japanese soroban, by Takashi Kojima; that I first acquired in the early 1970s when I began my abacus journey. The photo is also accompanied by a contemporary Chinese-made teacher's abacus, designed so the beads stay put when hung vertically for the classroom:

A Brief Primer on Soroban Addition:

Performing addition and subtraction (the inverse of addition) efficiently on the soroban means quickly determining which kind of operation you need to perform. Though I'm not a master soroban operator, I can work my way around the beads well enough for my purposes, enough to know that I often can enter each number without consciously thinking how I did it, through rote practice. But I've since analyzed my methods, and have determined the following procedure for beginners to follow for addition on the beads. This procedure is based on Kojima's teachings, but expressed in logical steps for the western adult-brained learner.

Firstly, you do need to know the fives and tens complements.

Next are a series of questions you need to ask, in the order listed, when confronted with a single-digit addition problem:

A) Can the number be directly added? If yes: add the number, problem done. If no, go to step B. (Examples of this kind of problem: 1 + 3 and 2 + 7)

B) Are both numbers less than five? If yes, subtract the five complement of the number and add a five bead (this is done with one swift downward move of the index finger), problem done. If no, go to step C. (Examples of this kind of problem: 4 + 3 and 3 + 2)

C) Can the tens complement be directly subtracted? If yes, subtract the tens complement and add a bead on the next rod to the left, problem done. If no, go to step D. (Examples of this kind of problem: 3 + 8 and 9 + 6)

D) Push the number up, then add a bead on the next rod to the left. (Examples of this kind of problem: 5 + 9 and 7 + 6)

There is one more complication. Sometimes, when dealing with multi-digit numbers, when doing a tens complement problem and you need to add the single bead on the next rod to the left, if that rod already holds a value of either 4 or 9, you can't directly add that single bead. If the rod has a 4, you need to swipe down the five bead and all four ones beads (essentially doing a fives complement operation in order to add the single bead). If the rod has a value of 9, you have to clear the nine out and add the single bead to the next rod to its left.

I should also mention that when adding multi-digit numbers, you do so from left to right, like the order in which you would write or speak them. This is more efficient than the right-to-left paper method we were taught in school.

I know that for the rank beginner this all sounds complicated. But what I've described thus far is all you need to know to do addition problems involving numbers of any length. You do them one digit at a time, from left to right, using the rules I've described above.

Know also that I will be touching on this method in more depth in an upcoming video on my YouTube channel.

Removing and installing the platen was easier than expected - once I was able to loosen the left platen knob via a set of rubber strap wrenches, that is! I have Ted Munk to thank for sending me a page out of the service manual where it illustrates how to remove the platen:

I've yet to do any upgrades to the sound insulation inside the body panels, something that Ted has shown us how to do with his Brother project machine, but it should make this machine even quieter in use.

As for which ultra-portable in my collection is my favorite, perhaps that'll be the subject of another video. I still need to do more typing on this machine, and it also needs a darker ribbon, so I need to get an order placed (perhaps I'll get a bulk roll from Baco Ribbon Supply!). The favorite ultra-portable competition in my collection is between the Groma Kolibri, the Olympia Splendid 33 and this Mercury.

Here's Episode 300 of the Typewriter Video Series, about this project:

I was once a VCR and camcorder technician, back in the 1980s, when I was younger, had better eyesight and steadier hands. Even so, it was challenging, especially camcorders with their innards crammed with compact circuit boards connected together with fragile ribbon cables, and their miniature transport mechanisms that were a marvel of precision miniaturization. Electronic problems were approached using structured problem solving -- troubleshooting -- involving voltage and waveform measurements, assisted, if you were lucky, with service literature from the manufacturer.

But before these marvels of electronic and mechanical miniaturization there were all-mechanical cameras. Oscar Barnack, working for Leitz optics, around the WW1 timeframe invented the first practical rollfilm camera using 35mm motion picture film, which eventually became what we know as the Leica rangefinder. A dense, compact metal chassis crammed with precision machined parts and featuring rangefinder focusing mechanically coupled to jewel-like miniature lenses, Leica rangefinder cameras have remained even today the pinnacle of mechanical camera engineering. But back in the 1930s Soviet manufacturers began copying the early Leica screw-mount (so called "Barnack") rangefinder cameras, with sometimes dubious engineering and build-quality.

I've been using one of these, the Zorki 4, made in 1971, with its diminutive but elegant Jupiter 8 lens, since the 1980s. The camera has been remarkably reliable, considering I used to leave it in the glove box of my car, winter and summer; I've often wondered if its internals weren't lubricated with whale oil, because it never seems to have been bothered by the cold, despite its all-mechanical operation.

A few weeks ago my friend Ethan Moses began educating himself on Russian rangefinder cameras, by buying a handful of these old cameras from online auction sites. In the intervening time since they've arrived on his doorstep, he's learned to tear them down, service them and put them back together, mostly in better shape than when he started, with the exception of one or two early on that served as training aids. These all are, in some form or another, direct descendants (or knock-off clones) of Oscar Barnack's Leica, albeit with mostly inferior mechanicals. The Fed models (named after Felix E. Dzerzhinsky, head of the Soviet secret police) were the worst of the lot in terms of design and build quality, while the Zorki models were noticeably better. My camera, the Zorki 4, was probably the height of Soviet rangefinder camera technology, in terms of build-quality and features, but it is the little Zorki 1 that surprised both Ethan and I.

The Zorki 1 lacks the slow-speed timer mechanism of the later Zorki 4, meaning the slowest timed shutter speed is 1/25 sec. It also has separate rangefinder and viewfinder windows, meaning you first focus on your subject in the rangefinder window (by turning the lens focus ring and aligning the double images where you want the image to be most sharply focused), then move your eye to the viewfinder to frame your shot. The Zorki 1 also lacks the nifty adjustable eyepiece diopter of the Zorki 4, a boon to eyeglass wearers. But where the Zorki 1 lacks in features it makes up for in diminutive form factor. Compared next to each other, the Zorki 1 top plate barely pokes above the upper trim line of the much taller Zorki 4.

Ethan and Zorki 1 in hand

Though metallically and mechanically dense in heft, the Zorki 1 fits in the hand very comfortably and is easy to carry around, especially with a collapsible screw-mount lens attached. It also lacks strap lugs, meaning you either have to use the original leather case (which are rather rare), or attach a 1/4-20 strap lug fitting to the tripod socket. I think it feels best in hand sans strap altogether. Also lacking a built-in light meter, the best way to use these cameras is use a light meter app on your phone, take a reading, transfer the settings to the camera and then just go shooting and not worry about further metering unless the light significantly changes, relying instead on the exposure tolerance of film. The ultimate in simplicity.

I often hang out at Ethan's on Tuesdays, and these last few weeks I've watch him tear these cameras apart, describing to me each part's function, watching him learn the ropes as he becomes more adept at servicing them. Sometime after Ethan gained confidence in servicing Russian rangefinders he tried his hand at a Japanese-made Canon rangefinder.

In comparison to the more primitive Soviet cameras, the Canon seemed over-engineered in complexity, making it much more difficult to service. What makes this ironic is these Canon rangefinder cameras don't seem to garner the prices on the used market of the original German screw-mount Leicas, meaning there's little sense in buying one if it needs servicing, you're better off just getting a Leica instead.

Yet, despite the challenges, working on the Canon was a valuable education for both Ethan and I. Based on his past experience with the Soviet cameras, Ethan could identify each module of the Canon's mechanism, noting the similarities and differences in how specific functions were carried out.

The analogy that came to my mind as I observed Ethan tear down and rebuild these intricate mechanisms over the course of the last few weeks is that they serve as a form of mechanical logic: one linkage pawl gets held back by the slow-speed timer, preventing the second shutter curtain from releasing until the slow-speed clockwork winds down, then the second shutter curtain is released, ending the exposure. In a digital camera this logic would instead be performed by firmware in a silicon chip, but in these cameras the "programming" was strictly by means of an intricate interaction of mechanical parts.