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Time for another installment of "There's No Such Thing As A Slide Ruler".

Another day, another eBay entry in this category...but at least the seller was TRYING.

This time, he calls it a "Slide Rule Ruler, Slipstick". It's a single-item post, for a slide rule. He's on the right track, but the inclusion of "ruler" says to me that he doesn't really understand the device he's selling. He probably got it from an estate sale or as a bequest or something, and that's fine. So I sent him a friendly note letting him know that he didn't need to include the word "ruler", and that it could potentially obfuscate his SEO rather than improve it.

He wrote me back and said he'd put the correction in somewhere, but it wouldn't let him edit the title. That's fine with me. If he fails to sell it and winds up relisting it, maybe he'll leave out "ruler".

Good result, and I hope he makes a sale.

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I'm starting a series in this collection called "This Is Not A Slide Rule". There's all sorts of stuff that people call "slide rules" that simply aren't slide rules. I'm going to post pictures of what they think are slide rules and either properly identify it, and/or solicit commentary about it.

I've seen carpenter's rules, tape measures, and other such things called "slide rules" simply because they have a numeric scale and some piece on it moves or slides. This sub-collection won't contain those precalculated conversion tables with sliding sheets or revolving wheels used for specialized industrial purposes. Things like resistor color-code converters, English/Metric conversion tables, and weight/balance calculators for loading trucks, included under the general category of slide charts, wheel charts, or "Nomographs" or "Nomograms" are related to slide rules as they can perform specialized calculations, but aren't specifically "slide rules". I may someday create a collection specifically for such slide charts. (

This is also a different series from the "There's No Such Thing As A Slide Ruler" posts, that simply decry the mistaken confluence of "slide rule" and "ruler" that so makes me tear at my hair and headdesk.

First in this series of posts is an ebay offering of what the poster called a "German Steel Slide Rule". He couldn't make the sliding bit slide and "didn't want to force it". I sent him a nice note letting him know that what he had was NOT a slide rule.

Yes, it's a steel vernier caliper. Someone in the market for an old, somewhat rusty, steel vernier caliper would not find this one because it was listed in the "scientific instrument>slide rule" category.

To quote Doctor Smith, "Oh, the pain...the pain of it all..."


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Ok, pet peeve time.

I have a filter on eBay that sends me new listings every day. The filter looks for "slide rule" and "lot", the intent being to find the most cost-effective listings for my collection. I tend to get better deals when someone is selling multiple slide rules or slide rules with books, or other combinations. I've gotten a lot of good deals this way, including a box of a dozen beginners' rules, in the box from old stock, with their manuals and a vinyl case. Each rule cost me about $2.00. The intent is to give or lend the box of rules to someone teaching a class...or to someday teach such a class myself. But I digress.

The inclusion of "lot" in the filter description gets me listings where there's more than one item for sale. This is USUALLY useful, but sometimes can be frustrating. But the most frustrating is the listing by either an estate seller or someone who inherited grampa's business tools and wants to sell off the whole bundle. It was common for engineers to have drafting tools AND slide rules. One to do the calculations for a particular design, and the other to draw the design.

This does not mean that a slide rule is a "drafting tool". It also does not mean that a slide rule is a "ruler". There is no such thing as a "slide ruler". Even if it is a long, rectangular object with markings on it, it's not used for measuring length or distance, it's used to calculate mathematical or trigonometric values.

So it makes me want to tear out my hair when some bozo lists a bunch of old rulers, triangles, and squares along with a couple of slide rules as "drafting equipment". And it makes me want to repeatedly headdesk when they take a standard 12-inch ruler and a three-sided drafting ruler and combine them with a 10-inch Pickett or 5-inch Sterling and call it a "Lot of Vintage Rulers."

I don't want rulers. I won't USE rulers. I HAVE all the rulers I plan on using for the foreseeable future. I have nice ones, including one of those 3-sided ones, in my art supplies. If I need a specialized ruler, I'll buy one, probably from Dick Blick or a stationery store. I won't buy rulers when I'm looking for slide rules.

So, when I see some joker doing this on eBay, because he cluttered up my search filter, I send him a friendly and cheerful note informing him of his error, because he'll likely sell these items a lot more easily if he categorizes them correctly. A seeker of vintage rulers or drafting tools might likely turn down their listing if it includes two slide rules, because he doesn't NEED a slide rule, doesn't know how to USE a slide rule, and doesn't want to PAY for a slide rule. Likewise, a slide rule collector probably has no desire to buy a t-square, a set of triangles, a set of drafting dividers, compasses, and India ink pens, along with three drafting rulers, just to get a K&E Polyphase.

Maybe it's pointless. Maybe it's futile. Maybe it will just tick them off. But frankly, I don't care. Their mis-categorization is annoying and cluttering up my search filter with things that don't belong.

In this picture, they list a Westcott Typist Rule (not a drafting tool), that is a valid vintage item, since typewriters are largely obsolete. You can get this ruler on eBay for about $8-$10 before shipping. They also list a Falcon ruler, in centimeters. You can get a Falcon also for about $8.00. A Pickett Microline 140, with case, sells on its own for between $10 and $25. So this guy is selling two $8.00 rulers and one $20 (avg) slide rule for $20. He might get $36.00 if he sold them separately...and his listing wouldn't be clogging up my search filter! (ARG.)

Was this a silly rant? Yeah, mostly. But it's my OCD -- I don't like to see slide rules called rulers because they AREN'T rulers!


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Remember that K&D 68-1130 Deci-Lon pocket slide rule I got for just under $80, shipped?

I made out like a total BANDIT. Here's the proof.

This popped into my eBay search filter this morning.

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Here's the Deci-Lon pocket rule I snagged on eBay. The pictures are crap, but I'm tired, and don't feel like setting things up to take really good ones.

To recap, this one was listed incorrectly on eBay, the headline identifying it as a 68 1100 Deci-Lon. But that number corresponds with the 10" full-size rule, which is fairly common right now on eBay. The rule shown is the 68 1130, the 5" pocket size portable rule, and is much, MUCH harder to find at a decent price.

The only thing that keeps it from being a top-shelf slide rule purchase is the case. It didn't come with the standard leather case, but instead has a rather nicely-made padded fabric case, which you see beneath it. The pattern of the fabric is a bit unfortunate, and I can't tell if it's supposed to be tan or if it's just really, really dirty, but at least I have SOMETHING to keep the rule in to protect it from damage.

I've refused to buy the other 5" Deci-Lons on eBay, not because they're not nice rules -- they are -- but because of the PRICE. The AVERAGE price of a 5" Deci-Lon is between $150 and $200. I've seen one as low as $90 (with $9 shipping) ONCE, and it lasted only a few minutes before being snarfed up.

THIS one was less than $80, with free shipping. What kept it on the site long enough for my filter to notify me about it, and for me to check it out, was the incorrect title on the listing. I had to double-check the pictures they'd listed, to make sure they were in fact for the 5" rule, then snatched at it. For a wonder, not only was it low enough in price, with a wrong title that kept it available, but it also had a "Buy It Now" option! Usually, I miss the damned things because they're a regular auction, and I can't afford to pay what they eventually get up to.

This gets a nice bath, then a rubdown with Renaissance Wax. Probably tomorrow.
Pocket Deci-Lon 68-1130
Pocket Deci-Lon 68-1130

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Happy dance time!

I FINALLY got the slide rule I've been hoping to find for a reasonable price!

I love all of my slide rules, don't get me wrong. My Faber-Castell 2/83N is magnificent. But my selection of POCKET rules is a bit shy. The Faber-Castells with Addiators on the back, are among my favorites, as are a couple of the Picketts I got recently. The Acu-Math I got that isn't even on the Slide Rule Museum's page for the model is a real find, and is very beautiful now that I've done a restoration job on it. (The example on ISRM is made of celluloid and magnesium, it being a later version of the rule I have, which is celluloid over mahogany.)

But I've been jonesing for a Deci-Lon POCKET rule since I got into collecting slide rules. It's short and STUBBY, because it has just so Many SCALES! The thing is, lots of other people also jonesed for these rules, which makes their price skyrocket. They've been running between $125 and $200 for years. I tried to get one that came down to $80 + $12 in shipping, but it went in MINUTES. So yesterday, I happened to spot a new listing for a 68 1100 (that's the 10-inch rule) on Ebay. There was a problem, though...the picture was a 68 1130! So I double-checked. The pictures were a pocket rule...and the TEXT of the description said 68 1130, and that it was a pocket rule. In addition, they had a picture of the CASE, which was not the original, but a soft fabric case they'd made for it, and THAT is around 7 inches long, which means it HAS to be for a pocket rule. And last, but not least, was the price, only $80, with FREE SHIPPING.

The sound you just heard was the sonic boom from my YOINK!

It just shipped today. Unless there's a serious bit of scammery going on here, I should have my pocket Deci-Lon just in time for Christmas!

Here are the pictures the seller put online.
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I made a nice purchase on Ebay, a collection of slide rule documentation. There's all sorts, different models, different makes, different types. The seller was very kind, and collected them all in clear plastic sleeves in a 3-ring binder.

Didn't cost me very much, either...but if I give away a slide rule to someone, I like to include a manual if possible.

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I've been seeing a particular collection of compact technical books on Ebay for a while now. They started out at around $90 plus $13 for shipping, but I wasn't interested at that price. After that auction expired without a bite, it was relisted for $75 + shipping. Still was a bit rich for my taste, so I waited.

Sure enough, a few days ago, they were relisted at $40 for the set plus the shipping.


They arrived today and they are AMAZING books. They're in absolutely pristine condition for books printed around the time my parents were born! The bindings don't appear to have been bent at all. The pages have yellowed a little, but they're practically in mint condition. The creases on the foldout pages are crisp and even, and don't appear to have been folded back and forth a lot. The books give that new book crackle when you open the cover, and have that lovely old-book scent without any hint of mildew or dry rot.

Here's how the seller listed them:

For your consideration, an amazing set of Vintage International Textbook Company engineering books from the 1920's and 1930's. These are beautiful editions with black, embossed leatherette covers with gilt spines and blue marbled endpapers. There are detailed diagrams in each book.

Line Transmission and Calculations
Chemistry and Materials of Construction
Electric Elevators - ll
Mechanical Drawing
Alternations and AC Motors
Geometrical Drawing
Mechanical Principles
Electricity and Magnetism
Design of Direct - Current Machines
Elements Algebra
Practical Electrical Wiring
Electrical Measuring Instruments
Design of AC Machines - Transformers
Rectifiers - Converters -Motor Applications
Storage Batteries
Electric Elevators 1
Trigonometry - Slide Rule -Mechanics
Complex Quantities in AC Calculations
Electron Tubes - Control of Lighting Circuits

I looked them over and they are an incredible find. These can be the core of a magnificent technical library that can really help someone pull things together in the event of societal collapse. But they're also just fascinating to sit and read without a pressing need. They're the perfect food for the Elephant's Child.

Of course, there's one book on the Slide Rule. It also contains a full set of trig and log tables. You can see how pristine the foldout page is. All of the pages have that same, barely-yellowed cream color and mint-condition creases on the foldouts. I am pleased as punch to have snatched these up when the price came down!

Here's a link to the Wikipedia page on I.T.C., the publisher of these gems.
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The second of my acquisitions on eBay last week is a Pickett (more precisely, a Pickett & Eckel) 600-ES. It cost me a little more than a bare 600-ES would have, because I got it in the original box, with the original book, adjustment instructions, leather case, and serialized warranty card. They're all in excellent condition, and I took pictures of them all, below.

The green spool in the center of the first picture is a spool of finger-wrap I use when my fingertips get cracked from dry air. I used it as something to lean the rule against, but it slipped just as I was taking the picture. It looks okay, so I didn't delete the picture.

The rule itself was filthy dirty, the slide and cursor being almost glued in place with grime. I had to clean it carefully with dilute dish soap, scrubbing with a disposable toothbrush. Then I worked it over with Nevr-Dull wadding, polished it with a soft cloth until the metal polished clean and bright, then I waxed the entire thing with Renaissance Wax.

The case has some speckling on one side, probably from a sprinkle of water or coffee or something, but it didn't harm the integrity of the leather. I wiped it with a damp cloth to remove surface grime, then worked a penetrating leather-restoring oil paste called Garrison Gold into it, letting a thick coating soak in while I worked on the rule. I wiped it down with paper towels, then polished it with a microfiber cloth until it was shiny. There's no sign of brittleness, and the Garrison Gold should protect it from drying out.

Unfortunately, since this isn't the N600-ES model, just the 600-ES, it's likely not a model carried by astronauts, but it's still a nice acquisition.
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I made a few acquisitions lately, which I will detail in the next few posts.

I found an Acu-Math A-80 for a decent price (around $20, plus some shipping) on eBay, and it charmed me somehow. It's not a horribly fancy thing, but it does have a fraction-of-inch scale for converting to decimal equivalent on the back.

Now, what I've seen about the Acu-Math A-80 is that the rule is from the WWII period. The only example I've seen pictures of online are from the Slide Rule Museum, and the legend next to the pictures describes their 1945 example as "Early Vinyl clad Magnesium with finger pocket". But while their picture's finger pocket is grayish silver, the one I found has a BROWN finger pocket. Yes, this version of the A-80 is a more typical celluloid over mahogany, which dates it as pre-WWII, since during the war, mahogany wood was reserved for the war effort.

Magnesium wasn't used yet for military purposes because they didn't know how to keep it from burning if ignited. But a magnesium slide rule was a safe use, so Acu-Math switched to it for this rule in mid-production.

The one I got had some issues. The scales on the slide were starting to delaminate at the ends, so I had to very carefully use CA glue and some spring clamps to re-laminate the scales to the wood. This unfortunately left some surface marring on the face of the slide scales, but it wasn't a lasting problem, as I carefully re-polished, and incidentally de-yellowed the surfaces of the scales with a graduated set of plastic-polishing Scotchbrite-like pads. You can see the result below, returning the scales to nearly white, removing the CA glue marring, and restoring the entire surface to a uniform polish. I applied two coats of Renaissance Wax, let it dry thoroughly, and buffed it to a brilliant shine.

The slide was more than a little sticky, and it wasn't because it needed lubrication. The wood had ever so slightly warped, and there were a few places where the grain had lifted here and there. A couple made the cursor slide with difficulty in places, and others made the slide stick.

Some judicious work with 400-grit sandpaper, very carefully stroked in the tongues and grooves smoothed the wood back, and both cursor and slide now move smoothly. Renaissance Wax again came to the rescue, to seal the wood and lubricate it. It worked great, and the rule is now back in service shape. It wouldn't please a proper collector, since the rule isn't in original condition, but it's a very pretty thing and works perfectly.

Now I need to find a new case for it, since it didn't come with one. Maybe I need to learn to make them!
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