Missed opportunities


There was an interesting thread last week about lucky finds. Now, the other side of the coin: what was your most regretted missed opportunity?

For instance, I have just let this 10C go away:


I found the price a bit high (about US$ 90) and asked the seller a rebate, so did another prospective buyer... While we waited for a reply, someone else took it... If there is something rarer than a 10C, this is a 10C with a manual in Portuguese.

But considering that particular 10C didn't look so good ("the grapes are sour!"), this is not something to complain about.

The missed opportunity I regret most has to do with a classic pocket mechanical calculator, a like-new Curta calculator I disdained some years ago. When I was offered one for about $20, I tried it for a while and said that was not the kind of calculator I was interested in...


(No changes to the original posting, despite editing)

Edited: 7 May 2006, 5:12 p.m. after one or more responses were posted


I have a complicated attitude toward these great old machines. On the one hand, I'm a technology enthusiast who likes playing with systems. On the other, I'm a collector who appreciates fine examples of rare old machines. I find that my attitude toward the 10C clarifies my whole approach to the field, however. Several 10Cs have come and gone on eBay over the last couple of months. None of them seriously tempted me, though one or two might have been affordable. The reason is that the 10C sucks as a programmable. The enthusiast in me overrides the collector, and vetos the purchase because the machine wouldn't be much fun to play with.

On the other hand, a price of $90.00 might change the calculation. 8)



I agree. The HP10C lacks labels and subroutines. These lacking features make the HP11C run circles around the HP10C.


A lack of labels and subroutines didn't stop the HP25C becoming popular - what I find most restrictive is a lack of conditional tests

Mike T.


The reason is that the 10C sucks as a programmable.

Like the 12C, I think, and yet that's exactly what makes them kind of interesting. I mean the lack of basic programming resources may allow for unusual solutions otherwise would never have been tried. But I do agree the best available tools should always be chosen for serious and practical purposes. I'd never buy a 10C in 1983, when there were also the 11C, the 15C and the 41C to choose from.



Edited: 7 May 2006, 4:39 p.m.


Hi, Gerson,


Like the 12C, I think, and yet that's exactly what makes them kind of interesting. I mean the lack of basic programming resources may allow for unusual solutions otherwise would never have been tried.

You have a point there. But somehow the 10C still doesn't appeal to me. I have a vintage 12C, which does appeal to me. I think it's because that machine, in nearly identical outward form, is still being sold today. That gives the original additional interest to me as a collectable. On the other hand, I've heard it said that the 10C is rare because they were considered disposable. That doesn't increase their desirability for me.

What's funny to me is I continually try to come up with plausible objective reasons why I prefer this machine over that one. But the truth is, my preferences are mostly based on subjective things like "it's fun," or "it's cool." I can bend your ear for hours over what "fun" and "cool" mean to me. But what I have trouble doing is providing a succinct definition of either term. 8)



Hello Howard,

I can understand your point of view. So I won't try to convince you the 10C is worth acquiring, after all I haven't been able to convince myself to get that one... :-)

As of vintage calculators, I like the 15C because it was my first HP calculator ever. But I wouldn't use it today for, say, solving a complex linear system as my 42S does it much better.

Best regards,



My "missed opportunities" are fairly minor, as those go...

Several years ago, I bought an HP-71B, and later got a Surveying Module with no manual for under US$30. Unfortuntaley, no scan of the manual is on the MoHPC CD/DVD set.

For more than a year, I never saw offered on eBay any 71B Surveying manual or package including one. Then, in a span of a few months, three separate auctions for 71B's with Surveying ROM's and manuals were offered. The first two had high-value extras, but were very expensive. On the third one, I forgot to get my final bid in, and it went for only $108.

Still looking to get that manual...

I also didn't bid very aggressively on a HP-41 Solar Engineering solutions book, and it went for US$33 -- a bit less than I was willing to pay. I have a scan from another CD/DVD set (not MoHPC), but the wand desn't read the prints of the bar codes very well.

It was the only Solar Engineering solutions book I've ever seen offered so far...


Hi, Gerson;

I bought an HP10C some months ago (thanks, E.V.) and I did not regret. You see, the HP10C was the low-end Voyager, and many of them were bought to be given as gifts. I had a classmate (late 80's) that had an HP10C that his father was given as Xmas gift by Xerox, where he worked at that time. I remember I saw it and found no interest because I had an HP15C. About a year later he told me he forgot the calculator somewhere, maybe he dropped it in a bus. I asked if he would keep the manual, and he simply gave it to me telling "It'll be a lot more usefull in your hands, now." Well, the HP10C I bought had no manual neither box, only the original protective cover (and three new batteries! Thanks again, E.V.), but it was indeed in great shape. I keep it with the other Voyagers, now I have at least one complete series. Well, if we count the HP12C Prestige as part of the team, then I'll need one, though...

A few days ago I wrote a 33-step program that allows the HP10C to compute the four basic arithmetic operations with complex numbers. Subtraction is performed through addition with the second number entered as negative, and division computes reciprocal separately. It was just a good exercise, I enjoyed it.


Luiz (Brazil)


A few days ago I wrote a 33-step program that allows the HP10C to compute the four basic arithmetic operations with complex numbers.


It was just a good exercise, I enjoyed it.

Hello Luiz,

That's a good example of using these calculators as programming exercises. I have to remember to try this on the 33C :-)

Back to the 10C, do you remember having seen them at stores? Were there many of them? I never saw a 10C or a 16C on sale here.




Hi, Gerson;

The HP16C was not sold in Brazil. Market research (who knows who made them) showed there would be not enough buyers. I have some Voyager promotional folders in Portuguese (Brazil). One of them shows only the HP11C and the HP15C, one other shows the HP10C, the HP11C and the HP15C, others show the HP12C, and I have two detailed folders, four pages each, one for the HP11C and the other for the HP12C. None of them show the HP16C. I called HP in Brazil and asked them about the HP16C. They confirmed it was not sold here, neither was the HP41CX. These two are actually rare, here.

I never saw an HP10C for sale in any store, and I actually have never seen an HP10C manual in Portuguese. I only saw two of them (prior to have my own): the one I mentioned in my previous post, and another one, with an Engineer that asked me how to enter in Complex mode... He thought the HP10C had the same functionality with complex numbers available with the HP15C. Go figure...

Another calculator that had a short lifetime in Brazil was the HP38G. I tried finding one in Rio de Janeiro and I was told that they sold only three units (didn't ask the time they wait to), and that the remaining units were returned back to HP.


Luiz (Brazil)

Edited: 7 May 2006, 10:58 p.m.


Gerson --

I've posted at length several times about the HP-10C. In many ways, it was a substandard product that today exemplifies one of the paradoxes of collecting: Something from the past is now expensive to obtain -- because it is rare -- because not many were ever sold -- because it was rather undesirable or flawed in its day. Ergo, bad => expensive. Another example is the Edsel line of cars from Ford in the U.S. during the late 1950's.

The HP-10C shares the nice form factor and high build quality of the Voyager line. However, it still had a rather high list price of US$80 (compared to its competition), albeit lower than the much-better HP-11C and HP-15C. The HP-10C was offered from 1982-1984, while the other four scientific Voyager models were offered until 1989.

The basic flaw of the HP-10C was that it offered the crude programming capabilites of the HP-12C (borrowed from the short-lived HP-55, I believe), in place of useful mathematical functions that were omitted, due to its single shift-key simplicity. I think it would have been better as a non-programmable with a few more functions and a "backspace" key as the other three Voyagers and the HP-41 had.

I got a very nice HP-10C through eBay about 15 months ago in order to complete my Voyager collection. I admit having paid the highest price of any single calculator (excluding accessories) in my collection for it.

Here are several past threads on the topic:



-- KS

Edited: 7 May 2006, 10:43 p.m.


Hello Karl,

It appears the HP-10C is the last item in every one's Voyager collection. Mine still lacks the HP-10C and the HP-16C. I had the chance to get both of them locally, where they are cheaper, but I didn't because I was not so sure about their quality. Anyway, I think I should have purchased them. If they were not so good as my HP-11C below, I just could resell them at eBay. By the way, that was my strategy to get this HP-11C: I purchased three of them, kept the best looking one and sold the other two (kind of a hassle though).

Thanks for the interesting links.




I bought an HP-10C when I was in college. It was a nice second calculator, in addition to my HP-28S; it was particularly nice for use on exams, because its simplicity meant no distractions; it didn't cause raised eyebrows from the proctors, and its programmability was just enough to help with plotting functions and numerical root finding.

Too bad I don't have it anymore! I sometimes miss the elegant simplicity of the thing. And, of course it never occurred to me that it would become a sought-after collectible one day!

- Thomas



Now, the other side of the coin: what was your most regretted missed opportunity?

Not to have bought a Curta immediately after the article appeared on Scientific American. I knew the price would explode here in Germany too, once the translated article would have come out in "Spektrum der Wissenschaft" two or three months later...
Unfortunately, I didn't have the 200 or so Euros to spare at that time - and now, with prices reaching 1000 Euros I will have to live without a Curta forever :-(

Greetings, Max

NB: My greatest missed opportunity HP-wise was a 41C with a box of accessories on a flea market that got sold very, very cheaply to a guy who was in the "queue" just in front of me ...


About the time they were discontinued a local HP retailer had a few dozen of the HP10C's on closeout. Several months went by and they were not selling. I wanted to make an offer on the lot but couldn't see far enough into the future...


I knew the price would explode here in Germany too, once the translated article would have come out in "Spektrum der Wissenschaft" two or three months later...

Now that Scientific American stated that "FABER-CASTELL 2/83N slide rule is considered by some to be the finest and most beautiful slide rule ever made", I wonder those who might want it will have trouble getting one for a reasonable price.




I started my slide rule collection many years ago. At the time slide rules were priced at giveaway levels even in antique stores. Then the New York Times published an article saying that slide rules were collectibles. Prices increased practically overnight. It was a two edged sword. While obtaining additional slide rules for my collection became more expensive the value of my collection had increased. The pride of my collection is still the K&E Log Log Duplex Decitrig that I purchased as a freshman engineering student in 1946. The slide rule is somewhat used but the accompanying manual is near mint condition. In those days no self respecting engineering student would admit that he had to read the slide rule manual.


I took the last Slide rule course, a 1 unit class concurrent with Chemistry in 1974 at ELAC college. I bought a Pickett Circular slide rule and a K an E Log-Log trig rule. I paid $35.00 for the Slip stick. A week later they went on sale. There was a bargain table piled high with slide rules for $5.00 a piece with leather cases. The calculators had started hitting the display cases. TI SR50 for $150, HP 35 for $295. I gave my Credit card a true workout and purchased a HP 35. Took 18 mos to pay it off.

I felt the Circular sliderule was much easier to use than the slip stick. I have several in my collection.

The following semester, Calculator classes replaced the Slide rule classes.

I have seen the Russian pocket watch style slide rules on e-bay and they look quite elegant.

Warmest regards,

Babyboomer Aerospace engineer


This is my only slide rule. I was given this one some years ago by a work colleague, now retired, who purchased it in 1974 when he started his Electrical Engineering course. He never had to use it as scientific calculators (at least CASIO calculators made in Japan) had become affordable by the time his classes started.

It is complete with leather case and manual. Of course, I don't need to read it... for multiplying and dividing :-)


Too many to count. 8``^(


I was working for HP in England in the late 1970s or early 80s when they discontinued the HP01 calculator watch. To clear stock HP staff were offered the opportunity to purchase one gold unit and one silver unit for a special staff price of $100 each (complete new units with the pen, box and everything else) For some reason I didnt take up my option and have regretted it ever since!

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