Please note that the merchandise below is not for sale! Auctionbandits is dedicated to helping you learn how to make money on eBay, and one of the best ways I can think of to do that is to give you some real-world examples of what those millions of eBay buyers out there would love to buy from you!

Hewlett Packard HP-41C calculator, vintage 1979, $6.

Taking some time to learn at least a bit about the area of vintage pocket calculators - specifically Hewlett Packard pocket calculators - is one of the most important steps you can take toward making money in this business. Since 1970s vintage HP models like this HP-41c  are prized by collectors around the World, and since they appear regularly at yard sales, flea markets and estate sales across the country, the opportunity should be clear!

When we think of pocket calculators nowadays, we don't normally think big money. Okay, we do see those high-powered Texas Instruments graphing calculators in the stores that cost over a hundred bucks, but when you consider everything they can do, they're not really that bad of a deal. As a matter of fact, I always keep an eye out for the TI-8X series of graphing calculators because I can buy them for a couple of dollars and sell them for much more on eBay. The vast majority of calculators that appear at yard sales, though, are cheapo pieces of trash that aren't even worth picking up. It's unfortunate that so many good, dependable workhorse calculators that cost a bundle to buy new won't even bring $5 on eBay nowadays.

What's really interesting about this particular entry is that even the weird little world of the pocket calculator has its own 'sweet spot' that the Auctionbandit can exploit. By sweet spot, I'm referring to the fact that there's a certain type of calculator you can find for very little money, which your Bayer buyers will pay you very well for, but which very few people besides you and the collectors who will buy from you even know exists. I'm referring to the vintage Hewlett Packard pocket calculator, and it's one of the quintessential Auctionbandits sweet spots. By the way, In this entry I'll often refer to Hewlett Packard as simply "HP" to shorten things up a bit.

I'm not going to go into painful detail about just why people collect Hewlett Packard calculators made from 1968 through 1986, because there are countless websites, like, which are dedicated to the old HP calculators and can explain things to you much more clearly than I could here. My job is to help you make money wherever money can be made, and I do that by: making you aware of the fact that these old HP calculators are very collectable and are out there waiting for you, and by familiarizing you with what they look like so that you'll know them when you see them.

One thing I should get out of the way first is the subject of the newer Hewlett Packard calculators. HP has made some very inexpensive calculators, like the HP-10B business calculator, for example, which you'll see floating around at yard sales and flea markets. Likewise, they've made made some really expensive contemporary models as well, like the 48GX and the 42S.

The problem is that unlike the cheaper models of the newer HP calculators, you're unlikely to ever run across the expensive ones, much less have the opportunity to grab them for a couple of dollars. Learn to spot them if you like, but you'll probably forget their designations before you find one. The older HP calculators, on the other hand, are out there, they have a very distinctive look to them, and you can pick them up for almost nothing since the people selling them rarely know what they cost new or how desirable they are today.

The sweet spot here may be even sweeter than you imagined. The people who collect these old calculators know that these critters are at least twenty years old, which means that they'll likely have problems, and may not even work anymore. But that's no big deal at all for these collectors, many of whom are quite capable of tearing these old HP calculators apart and fixing them as good as new. And you know what that means? Right - it means that even broken calculators will be snapped up, either to be fixed or to be used for parts to fix other calculators. And remember that collectors, being what they are, are also after owner's manuals, wall chargers, expansion modules, literature and all sorts of other pieces, parts and boxes having to do with these old HP calculators. So - consider yourself notified that every shred of anything having to do with a vintage Hewlett Packard calculator will have someone on eBay looking for it.

I guess the next logical question is, just how old is old? Officially, collectors are primarily out after stuff made between the years of 1968 through 1986, and if these old calculators had their dates of manufacture stamped across the back, life would be much easier, wouldn't it? But they don't, so it helps to have a few visual indicators to go by so you'll know when you're looking at a calculator of interest. Let's take a look at a few earmarks you can use to spot the ones you want.

The first thing to determine is that the calculator you're holding is actually made by Hewlett Packard. This may sound silly, but some of those old Texas Instruments calculators can be pretty seductive, with all their buttons and expensive looks. Unfortunately, they're completely worthless. Except for some really unusual examples, older electronic calculators other than the Hewlett Packards simply aren't worth bothering with. As I write this, for example, the highest price on eBay's closed auctions for a vintage Texas Instruments calculator is $38, which should tell you how collectors view this mark.

If the calculator's display is translucent red plastic, I know that if I were to turn the calculator on - and I say this because many of these really older examples won't turn on at all - I'd be greeted with red LED numbers, instead of the more modern black liquid crystal numbers we see in newer calculators. A red display tells me that I'm most likely looking at an HP from around 1978 or earlier, a definite buy.

I also look for the tan colored body, which was used on many HP models until around 1976 or 1977, another go signal. Note that the HP-25 I stuck at the end of the photo montage above sports both the red display and the tan body.

Another earmark of a potential winner is a thick profile. Sure, some of the older HP calculators were ones thin like HP's contemporary models, but most of the old HP calculators were rather stout units about an inch thick, like our HP-41C (and the HP-25) above. So, whereas not all older HP calculators are thick, if the one I'm holding is thick, it's probably an older, more desirable one.

Something else I should mention are the yellow (and sometimes also blue) "function" keys that appear on so many HP calculators. The HP guys love to allocate several functions each key, which is very noticeable by the white, yellow and blue values allocated to each key. For example, notice how on our HP-41C, the RCL key also has a GTO function as well as an M function. If you want to recall something from the calculator's memory, for example, you simply press the RCL key. But, if you press the yellow function key before pressing the RCL key, you invoke the GTO function, which is used when programming the calculator, and tells the program to "go to" a specific step in the programming process. The HP-41C is interesting in that it allows you to type letters as well as numbers, so if you press the ALPHA key in the upper right corner before pressing the RCL key, you get the letter "M" on the screen. See how it works? On some older HP models, like the HP-25 for example, there's a yellow and a blue function key, and you simply press the appropriate color of function key, if required, to invoke the value of any given key.

Now, here's a very helpful tip. Back in 1981, HP introduced the 10C series of calculators, which included the HP-12C financial calculator, which has become HP's best selling calculator ever. Chances are good that if you haven't actually owned a 12C, you've seen one. And if you haven't seen one, by all means find a photo of one and memorize its wide, short profile. The reason I urge you to drill the HP-12C profile into your mind is because besides the model 12C, the 10C series also included the lesser known 10C, 11C, 12C, 15C and 16C calculators, all of which bring in excess of $300 on eBay! I hope you'll agree that's reason enough to commit the little HP-12C's profile to memory!

A strong suggestion is in order here. Always be sure to test every button on the calculator to ensure that they all have the correct tactile feel, and aren't "mushy" or sticky when pressed. This may sound like an insignificant thing, but the presence of mushy or sticking keys will matter to buyers. Imagine how irritating it would be to work on a computer keyboard with a key or two that stuck down or didn't feel "right" when depressed, and you get the picture. Whereas your bidders will understand completely that you can't test the actual functions of one of these complicated calculators, but since you don't have to really know anything about the calculator to perform this simple test, there's no excuse for not doing it for your bidders!

Finally, and I know I'm always going on about this, but it's really important - the very best way to familiarize yourself completely with all these collectable HP calculators is to check eBay's closed auctions, and especially sites like Get a feel for the models that attract the collectors, and when you're out there at the yard sales, when you least expect it, you'll find a beautiful little HP calculator with a $2 sticker on it, just begging to be passed on to a loving collector. And when that happens, I hope you'll also think of us here at Auctionbandits!

This Hewlett Packard HP-41c calculator sold on eBay for $141.

Photo of vintage 1979 Hewlett Packard HP-41C pocket scientific calculator