Concise Metric Symbols

By The Metric Maven

Bulldog Edition

My Stepfather sent me an interesting metric artifact that reminds me of the Rosetta Stone. First a bit of background.  It was not uncommon in the past that plastic 75 mm x 110 mm card-like cases, which have a plastic card inside of them, with technical information were available for sale, and for institutional promotion. A good college friend had one that I was jonesen for in the worst way. I did make a photocopy of it, well part of one side of it. I have taken a photo and the image is below. I was completely enamored, but had no idea how to obtain one, and my friend could not recall where she obtained it. The amount of information on this small plastic card was amazing, and with young eyes, provided easy access for any science or engineering exam.

The edge of this image of the plastic card has a copyright symbol, a year, 1968, and Concise International CO., LTD. The internet has made any esoteric item’s history easily found. The Smithsonian has a page with the exact model my friend owns. It is the Concise 6000 Science Tables and Circular Slide Rule:

Concise Science Tables and Circular Slide Rule – Front View

The outer plastic case has a four inch rule on one side, and a 10 cm (tsk…tsk) or 100 mm on the other. The front has a circular slide rule, and the back a copy of the periodic table of the elements. At the top of the table is a Fahrenheit to Celsius conversion chart. The plastic card inside contains an incredible amount of mathematical, chemical and physical data, as well as conversion factors. The International Slide Rule Museum
has an eclectic group of Concise products. They were made for a number of technical institutions as promotional items. I was quite interested in the one which was created for electrical engineers:

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There are many different versions shown online, but my Stepfather sent me one that is unique to me. The front side of the plastic cover is shown below:

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I have essentially zero understanding of the Japanese language, so the ideographs for metric quantities caught my attention immediately. Below are the symbols for lengths.

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What is interesting is the symbol for meter is a single character. That character has another to the right of the meter symbol for millimeter, and a different symbol to the right for Kilometer. The values are nice and concise and seem metric in form, but the prefix is on the suffix side. The symbols for inch, foot, yard, chain and mile require three symbols it appears. They are clearly foreign to the Japanese and require more description than their metric counterparts. The Japanese lengths tend to have more compact symbols, but not always. According to Wikipedia the values are:

bu = 3.03 mm

sun = 30.3 mm

shaku = 303 mm

ken = 1818 mm

cho = 109.1 meters

ri = 3.927 Kilometers

The values for mass are given as:

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We can see the carat has a very complex symbol. The symbol for the gram is distinctive and follows a similar suffix rather than prefix location for modifying the gram. Despite the designation of t for tonne, the symbol looks more like that for Megagram, Mg, and in my view should have been designated as such. The grain, ounce, pound (assuming US?) have complex symbols, and the long and short ton have even more complex looking symbols. The native Japanese mass values appear far more concise than the Ye Old English ones. Their values are:

fun = 375 mg

me = 3.75 g

kan = 3.75 Kg

kin = 600 grams

The back side of the card holder has more equivalent values:

The cubic and capacity are at bit curious:

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The symbol for liter has a nice look of a volume. The symbol is shown in the symbol for cubic centimeter, but it would have been nice to have it be a milliliter with a two symbol combination as with millimeter and Kilometer. The liter symbol appears to be included in  the symbol for cubic meter. Somehow there appears to be an understanding they are all equivalent to multiples of the volume of a liter. I will not attempt to offer values for the Japanese volumes.

The front of the interior plastic card has length and mass conversions:

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The back has area and volume equivalents.

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While the internet has made such conversion charts mostly obsolete, it is interesting to look at some of the archaic values. The one which is new to me is the register ton, which is equal to one hundred cubic feet. According to Wikipedia, this volume unit was used to describe a ship’s total interior volume.

It is interesting that even without any understanding of Japanese, they appear to have used a logical symbolism that can be, to a certain extent, teased from the context. Mathematics may be the universal language, but the metric system is the universal relationship between the physical world and mathematics—well—except in the US.

The Design of a Marking Rule

By The Metric Maven


I’ve discussed the design of rulers a few times before. I’ve always been amazed at the number of options which have been used to define their divisions, and label their values. The website BoingBoing introduced me to another option for ruler design-–stenciled holes. The Incra website has a  millimeter metric-only ruler with stenciled holes that allow a person to mark distances with great precision. I could not help but purchase a 300 mm version to see how well it works. To the left is the label which boasts that this rule is a new 300 mm long metric, albeit 300 MM on the label.

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The first thing one notices is that the numerical labels for the holes and slots bounce up and down. I suspect this was done with the intention that separating the numbers spatially, would make it easier to distinguish them. In my view, it tends to be a bit of a distraction, but this type of separation has been used on other rulers and seems workable. This is a minor concern as Incra offers millimeter-only rules of this type in the US, which is of great utility when other options are limited.

The rules are flexible enough to conform to many objects and allow for accurate marking.They are also essentially stencils, and without pressure, do not return to a flat planar state under their own weight when placed on a flat surface. They are not really designed for use as an everyday ruler, but are for woodworking projects and other designs which might need a conforming rule with precision measure.

Below is a close-up of the left end of the rule:

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Incra has a lot of marking options on these rules. They have openings that will just accommodate a 0.5 mm Pentel mechanical pencil lead. One must extend the pencil lead far enough out to protrude through the hole or slot as the outer lead guide is too large to fit. The zero marking spot on the left hand side of the rule for both the line and single dot markings is cut in half to maintain the best accuracy possible. In the case of the dots at the center they start with half and are stepped in case you want even more accuracy and option.

A video shows how certain versions of their rulers allow you to mark dots and lines with ease, but they tout their inch-length versions and only casually mention that metric versions are available. If a person misguidedly insists they must have both a US inch and millimeter scale, the best version in my view is the 10″ decimal/mm marking ruler. The top scale is millimeters which is a clue that metric is the preferred scale for measure. Below is the inch scale which is marked in tenths of an inch with 1/20″ openings between. Recall that a millimeter is about 1/25″ and is the most precise measurement increment on the scale.

Related essays:

The Design of Everyday Rulers

Stickin’ it to Yardsticks

The American “Metric Ruler”

America’s Fractional Mind


The Metric Maven has published a book titled The Dimensions of The Cosmos. It examines the basic quantities of the world from yocto to Yotta with a mixture of scientific anecdotes and may be purchased here.