HP vs. TI on eBay auctions


Hi There,

After selling more than 1,000 Texas Instruments calculators on that auction site, I put four days ago some HP calcs for sale.

Guess what? For most of my TI's I could predict the number of watchers, with my HP's it is completely different!


Texas Instruments ABLE (the rarest TI I ever auctioned): 54 watchers

Texas Instruments SR-60: 52 watcher

Texas Instruments SR-51 Mint-in-Box: 50 watcher

Most TI's have 3..20 watchers after 4 days on the site.

And now the HP's:

Hewlett Packard HP 55: 58 watchers after 4 days!!!

Hewlett Packard HP 35: 36 watchers...

Wow - I have to collect HP, too.

Have a great Sunday,


Joerg: You did collect HP calcs, but you're selling them off. What interests me are the prices the apf and national semiconductor have been bid up to so far. That is yet another proof of the superiority of RPN - it has no equal.

So it's not too late. You can still cancel your auctions and even buy the Corvus that someone is selling. Come to the Dark Side Joerg. It's postfixerific!


Dennis, you hit the nail on the head. The value of these calculators is not so much their branding as HP .vs. TI, but the fact that they are RPN. I bought a NIB complete NS 4615 similar to the one Joerg is selling for $13.45 + shipping. With about a day left in Joerg's auction, the price has already been bid up to $41, and the final winning bid will not doubt be higher. The notable difference between the auction I won and Joerg's is that my auction made no mention of RPN, whereas Joerg's has RPN featured prominently in the heading and throughout the description. Remember when Joerg sold the RPN module for a TI calculator; it sold for a freekin' fortune.


Good morning!

... but the fact that they are RPN.

Which makes me curious, if there is any statistics/estimate regarding the percentage (or rather parts per million...) of RPN calculators within the total calculator "population". Theoretically, RPN calculators should be more valuable than non-RPN calculators by that factor, if value is based on rarity as with other collectibles. That would immediately place a six to seven figure price tag on any RPN calculator, no matter who the manufacturer is :-)

Regards, max


Statistical analysis is only useful if it places proper boundary conditions on the model. Regardless of rarity, if the population of buyers that are willing or able to spend 6 to 7 figures on a collectable item is zero, then that particular item can never attain that price. Rather, I see the RPN attribute as an added factor to the relative value of the calculator, rather than an absolute determinant. Also, I see the population of calculator collectors for whom the RPN attribute is important to be very small relative to the total population of collectors. Some, such as Joerg, may even see it as a negative.

Update. The auction is over and the National Semiconductor 4615 that was advertised as "RPN" sold for $86, whereas I paid only $13.45 for mine, which was not described as "RPN". However, I am not suggesting that it is the only reason for the differing prices, since other factors such as a worldwide .vs. domestic sale and the fact that this seller (datamath-computer-museum) gets tremendous exposure when compared to the typical calculator seller. Still, I do contend that there are sufficient data points for other similar sales to conclude that there is a positive correlation between RPN and desirability/price. The same, of course, can also be said for Hewlett-Packard .vs. all others, and a non-HP brand RPN will probably never achieve some of the prices paid for the rarer HPs. Still, some vintage HPs such as the HP-45 are pretty much common as dirt, and can easily be found in good condition for under $100. The APF Mark 55, BTW, went for $128.50.

Edited: 19 Apr 2010, 5:55 p.m.


Thanks for the kudos...

FYI: I have for sure a nice stat about my auctions.
62% (!) of my calculators sold this year outside of the US.
These nine RPN auctions ended up in: Germany (4), Switzerland (1), France (1), Italy (1), Israel (1) and United States (1).

"Domestic only" would kill half of the bids immediately.

I moved in 2006 from Germany to the US and still remember how disappointing every single "domestic only" auction was.



Not to beat a dead horse, but just another example of the "HP" and "RPN" value factor. Today I received a totally mint Novus Mathematician PR 4515 in the mail, including the soft case and charger, all for $26 plus $5 shipping priority mail. It works perfectly, and the internal NiCad batteries still hold a charge. Again, this was a worldwide TAS auction which made no mention of RPN in the heading, although it was mentioned in the listing. It got only a total of 67 visits, many of them mine, and none of the other bidders appear to be international (non-US). Anyway, I now have 10 National Semiconductor/Novus RPN calculators in my collection, all in good working order, and most of the non-HP RPN chipsets are now represented in my collection.


Sorry I drove the bid up. I seem to end up second in most of the auctions I bid on! I guess I'm good for sellers <grin>. Enjoy, my friend!! Michael


So you collect non-HP RPN calculators also? Cool. Well, look at it this way, next time that model shows up on TAS, you won't have to worry about me bidding against you. ;>)

Anyway, this was peanuts when compared to the king's ransom I had to pay for the HP-70.


I'm so "bitten" that I collect most any unique calculator.... some junk, but I've also found that the very early calculators had a lot of thought put into them, especially if they were one of few models produced by a company. The Panasonic 850 I just bought is a great example. What interesting engineering! Modular, gold-plated contacts, magnetic reed switches, removable power pack, etc. One weakness... a flimsy switch contact. Allowed me to buy it cheap and fix it easy!



I didn't "collect" HP calculators, I came across them ;-))



I didn't "collect" HP calculators, I came across them ;-))

That's a good sign. To misquote Hunter S. Thompson:
"You don't look for RPN. RPN finds you when it thinks you're ready."



I can tell you from experience that vintage HP calculators have more followers, than vintage TI calculators, who are willing to pay more. I was selling the TI-66, TI-65, TI-95 and TI-74, which I considered to be good machines, at prices that were so so. If these machines were HP branded, the sale price would be at least double.




Yesterday a NEW-IN-BOX TI-95 (Auction 270561922264 on eBay.de) ended on eBay.de above US$ 300 ;-))

The same day a used but good looking one (230459621554 on eBay.de) ended for less than US$ 25 :-((



Yes, that is a telling comparison. For instance, no good working HP 71B would go for less than 100 as far as I can tell.


Wow - I have to collect HP, too.

May the Force be with you!



I'm not sure if my contacts at TI would appreciate it ;-))



Hallo Jörg,

I'm not sure if my contacts at TI would appreciate it

Maybe that's the root cause. Thus let's quote Queen: "It's time to break free!" - remember you're a free man having the right to pursuit happiness d;-)

Beste Grüße, Walter

P.S.: I can understand the attractivity of some algebraic calcs - HP-27 above all, but also some of TI's - their logic, however, is just so inconsistent and confusing ...

Edited: 20 Apr 2010, 12:38 a.m.



I have one HP 38E left and just started to play around with it.
A lovelly machine - I really like it. Feels much better than even the SR-51, one of my favorites.



Similar thing happened to me, but from the HP side ... a colleague donates a mint 1975 TI-SR-51-ii to me, knowing that I collect HP's. Not sure if this was a statement, or him not fully understanding what I collect!
It's complete in the box, looks kinda nice, works well, has those red LED's that I love on my HP's ... but Joerg tells me that it's worth only about US$30 or so! Much less than an 'equivalent' HP.
HP's just have no equal ;)
Cheers, Keith


Keith, the problem I've had with this "hobby" is that I can only afford to collect a limited number of HP's, even with the many duplicates I have.

At least with other brands, I can see them, feel them, use them, appreciate their diversity, all for mostly the cost of postage. I've bought many calculators from 1 cent to 5 dollars. Not great if all you collect is HP's, but enjoyable for me to expand the collection to "calculators" in general.

I've bought some industry-specific calculators that I've found interesting: Horse racing calculator, paper industry calculator, time clock calculator, etc., all for just a few dollars.

Still, there's my HP's, then there's all the rest.... but at least I can get, "all the rest" for the cost of one or two HP's....


A similar thing happened to me as well. A friend found a pristine (albeit with corroded battery terminals) TI-59 at a yard sale, complete with several software libraries, and gave it to me as a gift.

I just haven't had the enthusiasm to fix it up, and the prices for these things on eBay haven't helped any. It has been sitting forlornly in a bottom desk drawer since.


Well, now, it's time to get the enthusiasm to fix it up!! The 59 was an incredible machine, and though others had a lot of bad luck with the keyboards, my 59 lasted through most of my senior year in high school and all four years of college. It still works perfectly today... somehow the card reader didn't even go bad! It had an alphanumeric printer, making it my "computer" until the HP-71 came out. I re-wrote every computer assignment, every physics and statistics equation... well, most everything. It printed calendars, banners; did everything but play music. (My 71B does that.)

Most every one of them does need the card reader fixed, but it still can be powered up and experienced without a working card reader. Go experience!


Most every one of them does need the card reader fixed, but it still can be powered up and experienced without a working card reader. Go experience!

I got one on eBay a few months ago (my first) for $9. It was ugly BUT after a good cleaning it looks unused. Inspired by your story, I was emboldened to try the card reader (it came with the diagnostics card) and it worked!

I also got a TI-58c for $2 at a local thrift store, with a leather pouch and in beautiful shape. I rebuilt battery packs for it and the TI-59 and they are both now among my favourite calculators.


Nice. I can't imagine investing the "brain power" to really learn to use the machine again, with all the op codes and such, especially for me, having "returned" to RPN. But when I did "stray", it was only for the 59. So it will always hold a special place in my heart. The only times I came close to filling up the machine's memory was with programs heavy on alphanumerics, which took up a lot of steps. BTW, if you can pick up a PC-100A or C printer, they make the greatest noise when they print, and they print quite fast, considering...


Looks like your HP calculator auctions did well!!


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